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Footnote 6 There are now published reports of exacerbations of HZO in persons immunized with herpes zoster vaccine, in individuals with a prior history of herpes zoster ophthalmicus. An alternate character set was available which included the entire Greek alphabet and special symbols.

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FP is a flatbed plotter. Level I was single precision only and had a smaller set of commands. Level II introduced double precision floating point support and had a much wider set of commands. Lien —which presented lessons on programming with text and humorous cartoons, making the subjects very easy to understand. Lien wrote that it was "written specifically for people who don't know anything about computers I want you to have fun with your computer!

I don't want you to be afraid of it, because there is nothing to fear". The only error messages were: In order to maximize the code that could be crammed into 4K of memory users could enter abbreviations for reserved words. For example, writing " P. The cassette contains a "Cassette File" version on one side and a "disk file" version on the second side for disk system users which was to be saved to disk. Blackjack and backgammon came with the TRS for free, and at its debut Radio Shack offered four payroll, personal finance, and educational programs, all on cassette.

A critical 80 Micro review of a text adventure described it as "yet another example of Radio Shack's inability to deal with the consumer in a consumer's market". The magazine added, "Sadly, too, as with some other Radio Shack programs, the instructions seem to assume that the reader is either a child or an adult with the mentality of a slightly premature corned beef.

Green stated that year that although "there are more programs for the 80 than for all other systems combined" because of the computer's large market share, "Radio Shack can't advertise this because they are trying as hard as they can to keep this fact a secret from their customers. They don't want the TRS buyers to know that there is anything more than their handful of mediocre programs available", many of which "are disastrous and, I'm sure, doing tremendous damage to the industry".

TRS owners must be resourceful", reporting that the computer's "keyboard, video, and cassette" functionality were also undocumented. Despite the TRS's limited graphics and sound capability, independent software companies such as Big Five Software produced unlicensed versions of arcade games like Namco's Galaxian , Atari's Asteroids , and Exidy's Targ. There were also many games unique to the TRS, including shooters like Cosmic Fighter and Defence Command and strange experimental programs such as Dancing Demon , [64] a game in which the player composed a song for a devil and choreographed his dance steps to the music.

Utility software such as Stewart Software's Toolkit offered the first sorted directory, decoding or reset of passwords, and the ability to eliminate parts of TRSDOS that were not needed in order to free up floppy disk space. The last versions 6. He concluded that it "is not the only alternative for the aspiring personal computer user, but it is a strong contender.

He noted that while "just about every component of my TRS has taken a trip to the local store to be fixed", "none of that cost me anything; it wasn't even inconvenient, especially with local Radio Shacks all over the place Given the price of the TRS, Tandy's quality control is better than you'd expect.

Three years later Pournelle was less positive about the computer. It was always unreliable, and repeated trips to the local Radio Shack outlet didn't help. The problem was that Tandy cut corners".

I'm a little bitter about my experiences with Tandy. I had genuinely thought that the Model I was the machine of the future: Of course it was never that. First, Tandy tried to fence in Model I users through that goofy operating system, and then it wouldn't let Radio Shack stores sell non-Tandy software. It had never been all that well designed, and when sales took off much faster than anticipated, the quality control system couldn't cope.

Furthermore, a Model III with two floppy drives required the use of only one electrical outlet a two-drive Model I required five outlets: Shortly after the Model III's introduction, Model I production was discontinued as it did not comply with new FCC regulations as of January 1, regarding electromagnetic interference. Tandy distinguished between the high-end Model II [15] and Model III, describing the latter as "an administrative system, good for things like word processing, data management and VisiCalc operations" and suitable for small businesses.

Installations with 32k or 48k of RAM could be upgraded with floppy disk drive storage. There was space inside the computer cabinet for two full-height drives. Third-party suppliers offered double-sided and track drives, though to control them they had to modify the TRSDOS driver code or else furnish an alternative third-party DOS which could see below. The installation of floppy disk drives also required the computer's power supply to be upgraded.

There was no internal cooling fan in the Model III; it used passive convection cooling unless an unusual number of power-hungry expansions were installed internally, such as a hard disk drive, graphics board, speedup kit, RS board, etc. In addition, they were used by copy protection schemes.

This was primarily to avoid legal disputes with Randy Cook over ownership of the code as had occurred with Model I DOS and also because Radio Shack originally planned to include several features in the Model III such as 80 column text support that ended up not materializing. Two early versions, 1. Instead of displaying garbage on screen at power up, it displayed a "Diskette? This included at least one update that would write an Easter Egg message "Joe, you rummy buzzard" on an unused disk sector, which was reputedly a joke message left by a programmer in a beta version, but accidentally included in the production master.

Many application programs used the so-called "at key" the key with a commercial at symbol , while others used the key combination SHIFT-up arrow. Under LDOS typeahead was supported. The usual selection of add-ons and peripherals available for the Model I were offered: It could be programmed to play up to five voices with a range of six octaves stereophonically.

A great many Orch as it was often called music files were available for download from Compuserve. The Orch was licensed from a company called Software Affair, which also produced the Model I-compatible Orchestra from Although mostly intended as a disk-based computer, the Model III was available in a base cassette configuration with no disk hardware and only 16k of RAM.

Upgrading to a disk machine necessitated installing at least 32k of RAM, the disk controller board, and an additional power supply used for the disk drives. Many school administrators valued the Model III's all-in-one hardware design because it made it more difficult for students to "walk away with" components of the computer when the all-too-busy teachers weren't looking. He concluded, "If you're looking for a computer that's not too expensive but that performs well, you would be wise to test the Model III—you might end up buying it.

They're trying to market it as a business computer when the existing software is woefully inadequate. You run out of memory before you get going. They're selling a medical package that takes up nine disks. I think the Model III is a very poorly conceived machine. The Model 4's case also switched from spray-painted translucent plastic to molded plastic, ensuring that the coloring was permanent and not prone to peeling off.

The Model 4's first appearance in the Radio Shack catalog read as follows: Compare the price and features of our amazing new Model 4 to any other computer in its class. You'll find that for power, versatility, and convenience it is a true breakthrough. To add the same features to other computers, you'd have to pay a whole lot more. Model 4 features, including the internal speaker, are unavailable in Model III mode. Its ramdisk program was called Memdisk and could use the optional extra 64KB of ram, or a specified portion of the Z's main 64KB.

Installing the system on the Memdisk also speeded the computer's operation greatly, as system overlays would load from memory rather than from disk. TRSDOS also provided a print spooler that ran as a background task while other applications were in use; it could take little user memory in an expanded machine since it could use the extra 64KB as its buffer memory. A FORMS filter made tailored printouts possible for applications lacking capability for formatted printing.

A barebones non-symbolic machine language debugger was standard. It also lacked the commands for setting, resetting, and testing graphics blocks on the display. This is because the Model 4 interpreter's variable names could be up to 40 characters in length, and the Model III interpreter's variable names had to be one or two characters in length the interpreter would accept longer names but only the first two characters were significant for uniquely identifying the variable.

What this meant for the programmer converting his old Model III program into Model 4 BASIC was a great deal of tedious editing because Model III programmers, to save memory and speed execution, typically compacted their code by using two-character variable names and eliminating spaces separating variables and keywords.

This was a major headache for programmers maintaining code for business applications, and prompted many BASIC coders to homebrew a replacement capability. Later third-party software publishers made products available to fill the gap for non-programmers. For those programming in languages other than interpreted BASIC, but never updated for the Model 4, this was their only option for accessing the new Model 4 features Microsoft eventually updated their entire line of language products for the Model 4.

Interfacing with the computer's hardware was likewise done differently than previously had been usual practice. This made possible, for example, to "print" a document to a disk file so it could be printed at a later time when a printer was physically available.

This method also ensured consistent communication between memory resident modules attached to the OS's logical devices. Some applications programmers, however, did circumvent this device-independent approach by physically accessing the computer hardware. The most glaring example of this was Radio Shack itself when it produced its SuperScripsit word processor; their programmers insisted on having the infamous CTL routine built into the keyboard driver expressly for this purpose.

Another offender was Anitek Software's Lescript. These two applications would ignore any filter programs attached to the keyboard device, depriving the user of some capable terminate-and-stay-resident programs, such as Misosys' Sidekick-like Pro-WAM Window Application Manager.

The disk drive storage on the Model 4 was identical to the Model III, consisting of one or two single-sided full-height 5. An additional two drives could connected via the external floppy port. Any floppy drive with the Shugart-style pin interface could be used; thus it was possible to upgrade a Model 4 to use double-sided, 80 track, or even 3.

External hard disks were available using the computer's 50 pin expansion card-edge, which also permitted other external hardware requiring direct access to the Z80 buses. These could include Atari style joystick adapters or the line of data acquisition devices marketed by Alpha Products. A parallel printer could be added using another card-edge connector provided for this purpose.

An RS serial port was optional on the original versions of the Model 4. The keyboard had a control key, a Caps Lock key, and three function keys. It used the TRSDOS event tasker so operations that disable Z80 interrupts such as floppy disk access could result in missed keystrokes.

The video display actually required only bytes to render the 80x24 text screen; the remaining memory held the typeahead buffer and the code that accessed it. While this freed 3 KB of Z80 address space for programs, it was marginally slower than writing directly into video RAM.

However, some third-party memory expansion kits could not allow this. Due to the different screen resolution x pixels rather than x pixels , the block graphics characters were not of uniform height. The ten vertical pixels in each character cell were divided into three graphic blocks, the upper two of which were four pixels high, and the bottom graphics block took the remaining two vertical pixels. These irregular graphic blocks made video games in Model 4 mode somewhat unattractive; game programmers preferred running in Model III video mode.

A 40 character wide display mode was available using a double-width raster image. By manipulating the video hardware in machine code, the Model III video modes 64 and 32 character columns with 16 rows were available as well. An alternate character set was available which included the entire Greek alphabet and special symbols. As with the Model III, the Model 4 was available in a baseline model with no disk drives and only 16k. They used a 16kx1 DRAM known as the Unlike previous machines, the RS port was standard equipment and no longer an extra cost option.

The RS and printer ports were also moved to the back instead of the underside of the computer, making them more easily accessible.

Programs and files could also be transferred back and forth via an RS serial cable. Both the Model 4 and the Model came with terminal software as a built-in feature. The graphics screen memory was separate from the usual character screen, and the two could be displayed together or separately.

Since only 19, bytes are required to render a x pixel screen, the additional RAM on the Radio Shack board was available for windowing the viewable screen around a larger virtual area. In a company called H. It ran with a 6. The Hitachi CPU also executed many Z instructions in fewer clock cycles than the Zilog chip; 8Mhz performance was claimed but in reality most software realized a performance improvement of only 25 to 30 percent.

This group of instructions take 21 transition states per iteration to execute on a Z; on the HD they take only There were enthusiast created programs that could access the 's DMA channels to attain an even higher rate of data transfer. Each tone had 32 different durations it could be sounded for.

One Radio Shack spokesman described the Model 4's sound generator as "being intended for business alerts". The magazine concluded that the Model 4 "provides a lot of flexible computing power Radio Shack has a guaranteed winner". Starting from late , a revised version was produced which came to be known as the Gate Array Model 4 catalog number A. This change greatly reduced the chip count and allowed the circuitry for the Floppy Disk Controller and the RS serial port to be included on the CPU board making this new Model 4 a single-board computer, unlike the original The Gate Array machine shipped with a green video screen instead of the black-and-white screen, and the arrow keys on the keyboard were grouped together into a single cluster the old Model 4 had two arrows on each side.

Veteran TRS game players were quite unhappy with the new arrangement of arrow keys. The position of the RS port's DB connector was improved. On the non-gate version this pointed straight down at the surface on which the computer rested. The gate array's connector pointed directly to the computer's rear, making the cable connection much easier and reliable.

An improvement was made in the computer's speed of execution. This difference in operating speed made many third-party hardware modifications, particularly speedup kits, rather troublesome to install on the older Model 4s extant.

A "luggable" version known as the Model 4P September , Radio Shack catalog number is a self-contained unit with a case design similar to that of a portable sewing machine. It had all the features of the desktop Model 4 except for the ability to add two outboard floppy disk drives and the interface for cassette tape storage audio sent to the cassette port in Model III mode are sent to the internal speaker.

It was sold only with the two internal single-sided KB drives. It was later made with the Gate Array technology catalog number A. The TRS magazine 80 Micro published an article describing a simple motherboard modification to enable the installation of two external floppy drives.

From then on the computer would behave exactly like a Model III. The 4P had a slot for an internal modem board. The Radio Shack modem board used its own proprietary command set and only supported communications at baud. Later a third-party company called Teletrends produced a baud modem board that used the industry-standard Hayes AT command set. It had an internal fan; its compact design did not permit it to use passive convection cooling as did the desktop Model 4.

A notable aspect of the 4P's video display was the solid, fully formed appearance of its text characters. This resulted from the fact that its 9-inch screen had the same x resolution as the desktop's inch screen, producing a greater density of pixels. Tandy discontinued the 4P by spring , stating that "even though you won't find a more enthusiastic and devoted group of owners than our Model 4P folks, transportables just weren't moving well for any company that also sold a desktop version".

By it also sold the popular The company stated that year that although Tandy had discontinued the 4P and other Model 4 variants, it intended to produce the computer "until the marketplace tells us it is no longer a product" and promised "a new double-sided drive version this fall".

Rather than using a lever-style latch as had previous Model 4 drives various brands were used throughout its production run , the new drives used a twist-style latch that provided for more reliable clamping. They were actually half-height drives mounted with full-height faceplates. These drives could actually format 42 tracks or cylinders with no difficulty, though this was unadvertised and not officially approved by Tandy or Logical Systems.

This technique upped the available storage on each disk to KB. The Deskmate productivity suite was bundled with the 4D. It supplied simple applications including a word processor, filer, spreadsheet, calendar, and mail manager. It provided scores of enhanced features, the most important of which was the ability to handle file dates through December 31, Files were now time-stamped as well. TED's chief virtue was that it occupied only 3KB of disk space while offering decent cursor movement and block capabilities.

This is no small convenience for a system with only floppy disk storage. It was not branded as a Radio Shack product, however. This change in marketing resulted from Tandy corporation's desire to enhance its stature in the marketplace, because it was perceived by some in the computer press that the old "Radio Shack" moniker connoted an image of inferior quality.

Parts and repair service remained available for several years longer. There were several versions, and it was later split into a 'home' and a 'business' version, Genie I and II, and System Mark I and II, where the II would have a numeric keypad instead of the built-in cassette player.

Meritum from Poland was TRS compatible. Based also on Iron Curtain similar parts like U instead of Z From Wikipedia, the free encyclopedia. For other uses, see TRS disambiguation.

This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. July Learn how and when to remove this template message. Tinkerers Search for New Spiritual Home".

Retrieved August 3, Retrieved May 6, Retrieved February 28, Retrieved January 23, TRS architect reminisces about design project. San Diego Computer Society.

Retrieved February 26, Retrieved October 17, Retrieved 26 October The Galveston Daily News advertisement. Retrieved 6 October HWG also took note of the results of a Cochrane library review of studies published in June Footnote 1 that reviewed benefits and harms of a booster dose of HB vaccine when provided at more than five years after the completion of the recommended primary immunization schedule.

Following the review of the evidence and consultation at the NACI meeting on October 5 , the committee voted on specific recommendations. The description of relevant considerations, rationale for specific decisions, and knowledge gaps are described in the text of this update. HB virus HBV causes acute and chronic infection of the liver. Typical symptoms of acute infection include nausea, abdominal pain, fever and signs of liver dysfunction such as jaundice, dark urine, changes in stool colour and hepatomegaly.

Although the majority of individuals spontaneously clear the infection after 4 to 8 weeks, the risk of becoming a chronic carrier, potentially leading to cirrhosis and hepatocellular carcinoma, varies inversely with the age at which the infection occurs.

Adults with diabetes may be at greater risk of progression to chronic infection and more severe disease. Footnote 2 Footnote 3 Footnote 4 Footnote 5. Footnote 7 Footnote 8 Footnote 9 While the level of HB surface antigen antibodies anti-HBs is thought to be important for preventing acute infection, presence of immunologic memory is required for long-term protection.

Footnote 10 Footnote 11 Footnote 12 Footnote 13 Footnote 14 Footnote 15 Due to a long incubation period of 60—90 days on average, even in the absence of protective antibody levels, stimulation of memory cells by immunization following exposure to HBV is believed to result in an antibody response which is adequate for the prevention of acute infection. Evidence also suggests that, in previously immunized individuals with preserved T- and B-cell memory, breakthrough infection i.

Footnote 16 Footnote 17 Footnote A recently released analysis Footnote 22 confirmed this trend, noting a decrease in reported rates of acute HB cases from 1. Since , rates of reported cases of acute HB infection have remained below 1.

Substantial reductions in rates of reported acute HB have been noted also among those aged 30 to 39, whose eligibility for vaccine would have increased over that time period. Footnote 23 The rates for acute and chronic HB infection are observed to be higher in males than females. Footnote 24 Data collected between and for the population aged 14 to 79 indicate a prevalence of current HB infection of 0.

The proportion of adults with diagnosed diabetes increases with age, with the sharpest increase in prevalence occurring after the age of 45 years. Footnote 27 On average, between and , there were approximately 65, individuals age , , individuals age , , individuals age and , individuals age 65 and over living with diabetes in Canada. Footnote 28 Due to the implementation of universal infant and adolescent immunization programs, the majority of individuals under the age of 30 born in Canada are likely to have been vaccinated against HB.

There are in total 4 categories in the horizontal axis. The vertical axis starts at 0 and ends at 20 with ticks every 2 points. A multivariate analyses found adults 23 to 59 years of age with diabetes to have 2. The odds were 1. In the US, the reported coverage of adults 19 years of age and older with at least 3 doses of HB vaccine was Similar epidemiological data that would allow an estimate of the HB disease burden and risk of infection among individuals with diabetes is not currently available in Canada.

Additional details about the types and contents of HB-containing vaccines available for use in Canada are provided in CIG. A supplementary literature search of studies published since November and a request for additional data from HB vaccine manufacturers did not identify any evidence that would suggest reduced long-term vaccine efficacy following immunization in infancy or among HCWs.

In November and October , a comprehensive review of studies with up to 30 years of follow-up data was presented to WHO. Data on vaccination failures demonstrated that these events were rare and did not result in new clinical cases amongst the vaccinated population. The review did not find evidence for the need for a HB vaccine booster dose in routine immunization programmes. A meta-analysis of long-term protective effects of HB immunization in over 9, individuals that was published in reported similar findings.

Conducted by Poorolajal et al Footnote 35 , the study found that overall cumulative incidence of breakthrough infection using anti-HBc as a marker of infection up to 20 years following the receipt of 3 vaccine doses was 0. Variation among studies included in the meta-analysis ranged from 0 to 0. Cumulative incidence of infection was determined to be 0. In studies covering a 20 year period, only eight transient HBsAg seroconversions were recorded, with no individuals becoming chronic carriers.

Cumulative incidence of infection was 0. Footnote 2 Footnote 4 Footnote 36 Footnote 37 Prophylaxis with HB vaccine provided within one week of percutaneous or mucosal exposure to HB-positive blood and within two weeks of sexual exposure to HB-positive persons, has been demonstrated to be highly effective in preventing HB infection. Footnote 4 A literature search, review of recommendations from other jurisdictions and a request for unpublished data from vaccine manufacturers did not provide any new evidence concerning the efficacy of post-exposure prophylaxis PEP with HB vaccine and immune globulin HBIg.

In total, HWG reviewed 39 publications that reported data on the immune response following the administration of a HB booster dose in individuals who were immunized as infants. In all studies, virtually all individuals who did not reach seroprotective titres following the receipt of a booster dose were without detectable antibody levels at baseline. An analysis of data from 21 studies Footnote 38 Footnote 39 Footnote 40 Footnote 41 Footnote 42 Footnote 43 Footnote 44 Footnote 45 Footnote 46 Footnote 47 Footnote 48 Footnote 49 Footnote 50 Footnote 51 Footnote 52 Footnote 53 Footnote 54 Footnote 55 Footnote 56 Footnote 57 Footnote 58 in which anamnestic response was measured 10 to 23 years following primary immunization in infancy that was conducted by Hu et al.

Similar declining trends in antibody levels following booster immunization have also been reported in a meta-analysis of 29 studies involving more than 2, individuals. Based on the analysed data, study authors developed a prognostic model for estimating protection against HB infection up to 17 years post HB immunization in infancy. The study did not find any association between the age of first dose and booster immunization antibody levels. In addition to these findings, HWG also considered results from subsequently since September published studies that reported on post-booster immune response following immunization in infancy as well as unpublished data from a relevant Canadian trial.

Unpublished results Footnote 76 of a trial conducted in British Columbia that tested immune response persistence among adolescents 10 to 16 years of age following immunization in infancy using a 2, 4, 6 month schedule were also shared with the HWG. In this age group 1. In the 10 to 11 year age group that received a 2. In this group, No primary non-responders were observed in this cohort.

The investigators concluded that infant HB vaccination provides adequate protection throughout childhood but protection continuing well into adulthood is less certain than following adolescent immunization.

A study by Middleman A. Footnote 77 reported antibody response to booster vaccination in individuals 16 to 19 years who previously received 3 doses 2. Although seroprotection was similar between individuals whose primary series was initiated within 7 days of age and those immunized at 4 weeks or older, older age at first dose was associated with significantly higher GMT levels Study authors found seroprotective titres to be present in In the same population, Van Der Meeren et al.

Hudu et al Footnote 81 evaluated immunity against HB among undergraduate students 23 years after receiving one to three doses of HB vaccine at birth, 1 and 5 months of age.

Similarly, Chan et al. Of 69 students who received the booster immunization, 10 After receiving three booster doses, all students achieved seroprotective titres. Footnote 83 measured immune response in individuals following the administration of two different booster doses at 10 to 15 years after primary immunization 0,1,6.

A smaller European study conducted by Teoharov et al. Footnote 84 In another study conducted by Chen et al. Footnote 83 that used a combined Hepatitis A and B HAHB vaccine for booster immunization, similar seroresponse rates were reported as in children who received a HB vaccine booster.

In another study conducted in Taiwan by Chang et al. In a similar population-based cohort study conducted by Katoonizadeh et al, Footnote 86 a booster dose was provided to children aged 10 to 18 years who were born to a family with at least one HBsAg positive parent and immunized in infancy with three doses of HB vaccine. Four weeks after the receipt of the HB vaccine booster, Another study by Avdicova et al.

Two studies Footnote 89 Footnote 90 providing information about seroprotection in immunocompromised individuals were reviewed by the HWG. A study by Inaba et al. Prior to immunization, only At more than 5 years following post-HSCT immunization, Another meta-analysis of 12 studies measuring long-term immune responses to vaccination in HIV-infected patients follow-up ranging from 12 to months was conducted by Kerneis et al.

Information pertaining to the immunogenicity of HB vaccine in individuals with diabetes was also reviewed by the HWG. A systematic review of the literature Footnote 29 Footnote 91 Footnote 92 conducted by Schillie et al. The proportion protected was generally greatest among children, ranging from In adults, particularly those who were older, median seroprotection was lower among individuals with diabetes Similar to healthy adults, lowest seroprotection rates in these studies were reported among diabetic adults with chronic kidney disease ranging HB containing vaccines are well tolerated, with adverse reactions such as irritability, headache, fatigue and injection site reactions e.

In October , for the purpose of assessing safety outcomes in individuals with diabetes following HB vaccine administration, ACIP published a review of 12 studies. Footnote 93 None of the reviewed studies reported serious vaccine-related adverse events, although ACIP did note the very rare occurrence of anaphylaxis in yeast-sensitive individuals that was reported by the Institute of Medicine IOM.

NACI does not recommend routine booster doses of HB vaccine for immunocompetent individuals following the completion of a recommended HB immunization schedule given in infancy. NACI concludes that there is fair evidence to make this recommendation, based on the limited information available through epidemiological and literature reviews summarized in this statement. Continuous, long-term, assessment of enhanced epidemiological data for the appearance of acute disease or the HBsAg carrier state in immunized populations general population and groups-at-risk is required before revising current recommendations.

National enhanced surveillance systems should as a minimum include information on: NACI recommends that adults with diabetes need not be considered as a separate high risk group for immunization with HB vaccine.

American data suggest a higher prevalence of previous or current HB infection among adults with diabetes compared to adults without diabetes, but similar Canadian epidemiological data are lacking. As there are notable differences between health care systems in the USA and Canada, and there is no current indication of higher risk of infection for individuals with diabetes in the general Canadian population, NACI does not have sufficient evidence to consider these individuals a separate high risk group for immunization with HB containing vaccine.

NACI will continue to monitor the evidence as it evolves. For immunocompromised individuals, initial annual monitoring of HB antibody levels following HB immunization may be considered. Optimal timing and frequency of further serological testing should be based on the severity of the immunocompromised state and whether the risk of HB is still present. For individuals with chronic kidney disease and on dialysis who are known to respond sub-optimally to HB vaccination and in whom anti-HBs concentrations decline rapidly, NACI has previously recommended annual evaluation of HB antibody levels.

There are several authorized schedules for HB vaccines in Canada. Epidemiological information demonstrating failure of universal prenatal screening and routine immunization programs i. Am J Prev Med ; This statement was prepared by: Hepatitis Working Group Members: Henry Chair , Dr. Gemmill Chair , Dr. Quach Vice-Chair , Dr. Cole Canadian Immunization Committee , Dr. Moore Canadian Paediatric Society , Dr. Sartison Canadian Immunization Committee. You will not receive a reply. Skip to main content Skip to "About this site".

Epidemiology of Hepatitis B IV. Please refer to the remainder of the Statement for details 1. Public Health Agency of Canada Published: Who This Statement addresses whether there is a need for HB re-immunization of adolescents who have received routine immunization in infancy, risk of HB infection in people with diabetes and timing of re-vaccination of people with immunocompromising conditions.

How Although decline of antibody levels may be observed over time, long-term protection and prevention of chronic infection is dependent on the presence of T- and B-cell memory. Why The majority of acute cases occur in unimmunized household contacts of a HB carrier and in people 30 years of age and older who acquire infection through unprotected sexual activity, sharing injection drug equipment or procedures with percutaneous exposure.

Providing an overview of current HB epidemiology in Canada and national sources of HB-related surveillance Reviewing evidence pertaining to primary and booster immunization in those vaccinated as infants and in individuals with diabetes and immunocompromising conditions Reviewing evidence pertaining to indications for HB immunoglobulin HBIg administration Making recommendations regarding existing HB immunization schedules, serological testing of immunocompromised persons, and surveillance and research priorities The primary goal of the statement is to provide further guidance on the need for re-immunization of adolescents who have received routine immunization with a HB containing vaccine in infancy.

Methods The NACI Hepatitis Working Group HWG reviewed such considerations as the epidemiology, target populations, the safety, immunogenicity, efficacy, effectiveness of the vaccines, vaccine schedules, and other aspects of the overall immunization strategy.

Footnote 4 HB infection in adults with diabetes The proportion of adults with diagnosed diabetes increases with age, with the sharpest increase in prevalence occurring after the age of 45 years. Text Equivalent - Figure 1 This is a column clustered chart.

There are 3 series in this graph. The vertical axis is "Percent. The title of series 2 is "" The minimum value is 0. The title of series 3 is "" The minimum value is 0.

Footnote 31 Similar epidemiological data that would allow an estimate of the HB disease burden and risk of infection among individuals with diabetes is not currently available in Canada.

Footnote 88 Two studies Footnote 89 Footnote 90 providing information about seroprotection in immunocompromised individuals were reviewed by the HWG. Footnote 4 In October , for the purpose of assessing safety outcomes in individuals with diabetes following HB vaccine administration, ACIP published a review of 12 studies. NACI Evidence Grade B Recommendation NACI concludes that there is fair evidence to make this recommendation, based on the limited information available through epidemiological and literature reviews summarized in this statement.

NACI Evidence Grade B Recommendation Optimal timing and frequency of further serological testing should be based on the severity of the immunocompromised state and whether the risk of HB is still present. Surveillance and research priorities Continuous monitoring of HB epidemiology in Canada including incidence and trends of acute and chronic disease Development and maintenance of enhanced surveillance systems that have the ability to capture cases of vaccine failure and breakthrough infection, particularly in high risk individuals Studies that aim to determine the duration of immunity and long-term correlates of protection, with particular focus on countries with low HB incidence Studies to determine the level of humoral, cellular anamnestic or both responses that are required for preventing chronic infection, and the timing of booster doses according to preserved anamnestic response Studies for evaluating the efficacy and effectiveness of Hepatitis B programs in long-term care facilities.

Differences in response to a hepatitis B vaccine booster dose among Alaska children and adolescents vaccinated during infancy. Footnote 46 Primary immunization: Three doses of recombinant 2.

Hepatitis B immunity in children vaccinated with recombinant hepatitis B vaccine beginning at birth: Vaccine, ; 25 Footnote 58 Primary immunization: Duration of hepatitis B immunity in low risk children receiving hepatitis B vaccinations from birth.

Pediatr Infect Dis J. Footnote 73 Primary series: Persistence of immunologic memory for twelve years in children given hepatitis B vaccine in infancy. Persistence of protection against hepatitis B virus infection among adolescents vaccinated with recombinant hepatitis B vaccine beginning at birth: Pediatr Infect Dis J, ; 27 Footnote 48 Primary immunization: