Recombinant hepatitis B vaccination of neonates and infants: emerging safety data from the Vaccine Adverse Event Reporting System

Childhood vaccination associated adverse events by sex: a literature review

BACKGROUND

Most approved medicines, including vaccines can be associated with adverse events. A vaccine adverse event is defined as any untoward medical occurrence which follows vaccination, but which does not necessarily have a causal relationship with the administration of the vaccine.

METHODS

The objective of this structured literature review is to analyse the adverse events reported with vaccinations usually done during childhood and adolescence: human papilloma virus vaccine, hepatitis B vaccine and measles-mumps-rubella vaccine. We evaluated the vaccine literature on children and adolescents by sex. We searched the Cochrane Database, Medline (Pubmed) and Embase using predefined terms.

RESULTS

Of the 417 publications retrieved from searches in the 3 databases, 89 papers (21%) were identified as potentially relevant to the review. On further scrutiny 41 of these satisfied the criteria for inclusion in the analysis. Serious adverse events related to vaccinations were rare. We found some possible sex related vaccine adverse events. Few trials however reported adverse events by age and sex and very few analyses evaluated the observed differences.

CONCLUSIONS

Despite earlier calls for sex-specific analyses of clinical studies, we found that vaccine trials were rarely reported and published by sex. Prospectively collated vaccine safety data in children and adolescents should be analysed by age and sex, so that clinical trial results can form an evidence base for vaccine practice recommendations.

Protective effect of hepatitis B vaccine combined with two-dose hepatitis B immunoglobulin on infants born to HBsAg-positive mothers

BACKGROUND

Despite the use of hepatitis B (HB) vaccine and hepatitis B immunoglobulin (HBIG), a portion of infants are still non- or low-responders, or even immunoprophylaxis failure. We aimed to determine the immune response in the infants from the mothers being positive for hepatitis B surface antigen (HBsAg), by which the infants received three doses of HB vaccine in combination with two-dose 200 IU HBIG injections.

METHODS

In this retrospective study, 621 infants from HBsAg-positive mothers in Beijing YouAn Hospital between January 2008 and December 2009 were included. All the infants were given three doses of 10 µg HB vaccine (at 0, 1 and 6 months of age) and two-dose of 200 IU HBIG (at birth and in 2 weeks of age). Serum HBsAg and antibody to HBsAg (anti-HBs) in all the infants were determined at 7 months of age.

RESULTS

Of the 621 infants, 2.9% were immunoprophylaxis failure (positive for HBsAg), 1.4% were non-responders (anti-HBs undetectable), 95.7% were responders. The 594 responders could be categorized into three subsets, 22 were 10 to 99 IU/L for anti-HBs levels, 191 were 100 to 999 IU/L, and 381 were ≥1000 IU/L. The immunoprophylaxis failure rate was at 0% and 5.2% for the infants of HBeAg-negative and HBeAg-positive mothers(P<0.001). Infants from mothers with detectable HBV DNA had higher incidence of immunoprophylaxis failure than those of mothers without detectable HBV DNA (P = 0.002). The factors including gender, birth weight, gestation weeks, the rates of maternal HBeAg-positive, and detectable HBV DNA did not contribute to the no response to HB vaccination.

CONCLUSIONS

Through vaccination by three doses of HB and two-dose of HBIG, majority of the infants (95.7%) achieved a protective level of anti-HBs at 7 months of age. Maternal HBeAg-positive and HBV DNA detectable were associated with the immunoprophylaxis failure, but not contribute to the non- or low-response to HB vaccination.

One arm or two? Concurrent administration of meningococcal C conjugate and hepatitis B vaccines in pre-teens

BACKGROUND

The purpose of this study was to: (a) compare rates of local reactions from meningococcal C conjugate (Neis Vac-C) and hepatitis B vaccines (Recombivax HB), and (b) compare local reactions when both injections were given in one arm versus one in each arm.

METHODS

Schools were randomized to have grade six students receive both vaccines in one arm (One Arm Group), or one vaccine in each arm (Two Arm Group; MCC always given in left arm). Structured telephone interviews of parents were conducted, and respondents were asked about local and systemic reactions, interference with school or other activities, need for medical attention, and lost parental work time.

FINDINGS

The Two Arm Group reported significantly more local redness >46 mm (6.5% vs. 0.5%, p < 0.001), moderate to severe tenderness (28% vs. 18%, p < 0.05), and drowsiness (14% vs. 7%, p < 0.05). When adjusted for sex, ethnicity, and town of residence, report of any tenderness was associated with town of residence only; moderate or severe tenderness was independently associated with the Two Arm Group (OR 1.4, 95% CI 1.1-1.85). There were no statistically significant differences between groups for interference with school attendance or other activities, need for medical attention, or lost parental work time. Among participants of the Two Arm Group (188 students), there was more redness (6% vs. 2%, p < 0.05) and tenderness (54% vs. 32%, p < 0.001) experienced with Neis Vac-C than with Recombivax HB, respectively.

CONCLUSIONS

Injecting two vaccines in one arm did not cause more local reaction than one injection in each arm and remains an option for those who prefer it for logistical reasons, If vaccinating in two arms, Neis Vac-C should preferentially be given in the nondominant arm.

Tracking vaccine lot lifecycles using reports to the vaccine adverse event reporting system (VAERS)

PURPOSE

There is currently no systematically available information available on how rapidly a specific lot of vaccine is used once distributed. We used data from reports to the Vaccine Adverse Event Reporting System (VAERS) to develop a proxy means of surveillance for the lifecycle of selected vaccine lots.

METHODS

A convenience sample, consisting of selected lots of: diphtheria, tetanus, and acellular pertussis (DTaP), Haemophilus influenzae type b (Hib), Hepatitis B, and varicella vaccines, was selected for lifecycle analysis. Assuming that circulation of a vaccine lot is proportional to vaccine-specific adverse event (AE) reporting for that vaccine type, we constructed Gamma distributed usage models and compared them with lot-specific VAERS reports to estimate the actual lifecycle of lots in the system.

RESULTS

Evidence of lot circulation was detected within 1-2 months, and a peak was observed 3-4 months after the vaccine release date for most of the study vaccines. Ninety percent of the vaccine doses in each lot were estimated to be used within 5-9 months of distribution. The length of time a vaccine lot was in use ranged from 5 to 17 months from earliest vaccination date.

CONCLUSIONS

Our modeled and inferred administration of the selected lots of different vaccines were concordant. This method may be useful for spatial and temporal tracking of vaccine lot utilization.

Hepatitis B immunisation for newborn infants of hepatitis B surface antigen-positive mothers

BACKGROUND

Hepatitis B vaccine and hepatitis B immunoglobulin are considered for newborn infants of HBsAg-positive mothers to prevent hepatitis B infection.

OBJECTIVES

To assess the beneficial and harmful effects of hepatitis B vaccines and hepatitis B immunoglobulin in newborn infants of HBsAg-positive mothers.

SEARCH STRATEGY

Trials were identified through The Cochrane Neonatal Group Controlled Trials Register, The Cochrane Hepato-Biliary Group Controlled Trials Register, The Cochrane Central Register of Controlled Trials in The Cochrane Library, MEDLINE, and EMBASE (until February 2004), authors of trials, and pharmaceutical companies.

SELECTION CRITERIA

Randomised clinical trials comparing: plasma-derived vaccine (PDV) or recombinant vaccine (RV) versus no intervention, placebo, or other active vaccines; hepatitis B immunoglobulin versus no intervention, placebo, or other control immunoglobulin; as well as PDV or RV plus hepatitis B immunoglobulin versus no intervention, placebo, or other control vaccines or immunoglobulin.

DATA COLLECTION AND ANALYSIS

Outcomes are assessed at maximal follow-up. The primary outcome measure was hepatitis B occurrence, based on a blood specimen positive for HBsAg, HBeAg, or antibody to hepatitis B core antigen (anti-HBc). Binary outcomes are reported as relative risks (RR) with 95% confidence interval (CI). Subgroup analyses were performed with regard to methodological quality of the trial, mother's HBe-Ag status, and time of immunisation after birth.

MAIN RESULTS

We identified 29 randomised clinical trials, five of which were considered high quality. Only three trials reported inclusion of hepatitis B e-antigen negative mothers. Compared with placebo/no intervention, vaccine reduced hepatitis B occurrence (RR 0.28, 95% confidence interval (CI) 0.20 to 0.40, 4 trials). No significant differences of hepatitis B occurrence were found comparing recombinant vaccine (RV) versus plasma-derived vaccine (PDV) (RR 1.00, 95% CI 0.71 to 1.42, 4 trials) and high-dose versus low-dose vaccine (PDV: RR 0.97, 95% CI 0.55 to 1.68, 3 trials; RV: RR 0.78, 95% CI 0.31 to 1.94, 1 trial). Compared with placebo/no intervention, hepatitis B immunoglobulin or the combination of vaccine plus hepatitis B immunoglobulin reduced hepatitis B occurrence (hepatitis B immunoglobulin: RR 0.50, 95% CI 0.41 to 0.60, 1 trial; PDV plus hepatitis B immunoglobulin: RR 0.08, 95% CI 0.03 to 0.17, 3 trials). Compared with vaccine, vaccine plus hepatitis B immunoglobulin reduced hepatitis B occurrence (RR 0.54, 95% CI 0.41 to 0.73, 10 trials). Hepatitis B vaccine and hepatitis B immunoglobulin seem safe, but few trials reported on adverse events.

AUTHORS' CONCLUSIONS

Vaccine, hepatitis B immunoglobulin, and vaccine plus hepatitis B immunoglobulin prevent hepatitis B occurrence in newborn infants of HBsAg positive mothers.

Effect of hepatitis B immunisation in newborn infants of mothers positive for hepatitis B surface antigen: systematic review and meta-analysis

OBJECTIVE

To evaluate the effects of hepatitis B vaccine and immunoglobulin in newborn infants of mothers positive for hepatitis B surface antigen.

DESIGN

Systematic review and meta-analysis of randomised clinical trials.

DATA SOURCES

Electronic databases and hand searches.

REVIEW METHODS

Randomised clinical trials were assessed for methodological quality. Meta-analysis was undertaken on three outcomes: the relative risks of hepatitis B occurrence, antibody levels to hepatitis B surface antigen, and adverse events.

RESULTS

29 randomised clinical trials were identified, five of which were considered high quality. Only three trials reported inclusion of mothers negative for hepatitis B e antigen. Compared with placebo or no intervention, vaccination reduced the occurrence of hepatitis B (relative risk 0.28, 95% confidence interval 0.20 to 0.40; four trials). No significant difference in hepatitis B occurrence was found between recombinant vaccine and plasma derived vaccine (1.00, 0.71 to 1.42; four trials) and between high dose versus low dose vaccine (plasma derived vaccine 0.97, 0.55 to 1.68, three trials; recombinant vaccine 0.78, 0.31 to 1.94, one trial). Compared with placebo or no intervention, hepatitis B immunoglobulin or the combination of plasma derived vaccine and hepatitis B immunoglobulin reduced hepatitis B occurrence (immunoglobulin 0.50, 0.41 to 0.60, one trial; vaccine and immunoglobulin 0.08, 0.03 to 0.17, three trials). Compared with vaccine alone, vaccine plus hepatitis B immunoglobulin reduced hepatitis B occurrence (0.54, 0.41 to 0.73; 10 trials). Hepatitis B vaccine and hepatitis B immunoglobulin seem safe, but few trials reported adverse events.

CONCLUSION

Hepatitis B vaccine, hepatitis B immunoglobulin, and vaccine plus immunoglobulin prevent hepatitis B occurrence in newborn infants of mothers positive for hepatitis B surface antigen.

Vaccination of yeast sensitive individuals: review of safety data in the US vaccine adverse event reporting system (VAERS)

The preparation of recombinant hepatitis B vaccines involves using cellular cultures of Saccharomyces cerevisiae, otherwise known as baker's yeast. Prior to vaccine licensure, clinical trials were performed to address whether residual yeast proteins in the vaccines could induce anaphylaxis, including testing for IgE anti-yeast antibody levels. 1-2% of subjects had anti-yeast IgE antibodies before immunization, but demonstrated no significant rise in IgE after HBV. We searched reports in the Vaccine Adverse Event Reporting System (VAERS) for those that mentioned a history of allergy to yeast and then reviewed the adverse events described in these reports for potential anaphylactic reactions. Probable anaphylaxis was defined as the presence of one or more dermatologic symptoms and one or more respiratory, gastrointestinal, or cardiovascular symptoms with onset within 4 h of Hepatitis B vaccination. Possible anaphylaxis was defined in one of two ways: (1) cases that described dermatologic or respiratory symptoms (but not both) occurring within 4h of vaccination; or (2) cases that described one or more dermatologic and/or respiratory symptoms occurring 4-12 h post vaccination. Among the 107 reports of pre-existing "yeast allergies," 11 reports described probable or possible anaphylaxis after HBV. Four additional cases were described after other vaccines. The majority of vaccinees who met the case definitions and had a history of yeast allergies were female, ages ranged from 10 to 64, and symptom onset ranged from 15 min to 5 h after vaccination. No deaths were reported. The small number of reports to VAERS may be partly due to health care professionals observing current contraindications by not vaccinating yeast sensitive individuals. Nevertheless, yeast associated anaphylaxis after HBV in sensitized patients appears to be a rare event.

Cutaneous adverse reactions following anti-infective vaccinations

Although widely administered, anti-infective vaccinations are rarely responsible for cutaneous adverse effects. In this context, hepatitis B and bacillus Calmette-Guerin vaccines are the most frequently incriminated products. Cutaneous adverse effects are less frequently encountered following administration of vaccines against varicella, diphtheria/tetanus/pertussis (primary and booster doses), measles, poliomyelitis, rubella, pneumococcus, tick-borne encephalitis, smallpox, Meningococcus and influenza. The adverse effects can occur at the site of or at a distance from the injection. The patho-mechanisms of local adverse cutaneous reactions include predominantly nonspecific lymphoid or granulomatous reactions. Allergic reactions to the vaccine strain, adjuvants, conservatives or other components are less frequently involved in local vaccine adverse effects. Systemic reactions are mainly mediated by immediate type or immune complex-related allergic reactions to toxoid-, ovalbumin-, gelatin- or pneumococcal-containing vaccines. Systemic reactions are sometimes related to a specific vaccine strain. Other cutaneous reactions may also occur through unknown patho-mechanisms. No vaccine type or strain is specifically associated with a particular type of cutaneous adverse effect. This article presents seven case reports of cutaneous adverse effects following anti-infective vaccination then reviews the relevant literature on this subject.

Understanding vaccine safety information from the Vaccine Adverse Event Reporting System

The Vaccine Adverse Event Reporting System (VAERS) is administered by the Food and Drug Administration and CDC and is a key component of postlicensure vaccine safety surveillance. Its primary function is to detect early warning signals and generate hypotheses about possible new vaccine adverse events or changes in frequency of known ones. VAERS is a passive surveillance system that relies on physicians and others to voluntarily submit reports of illness after vaccination. Manufacturers are required to report all adverse events of which they become aware. There are a number of well-described limitations of such reporting systems. These include, for example, variability in report quality, biased reporting, underreporting and the inability to determine whether a vaccine caused the adverse event in any individual report. Strengths of VAERS are that it is national in scope and timely. The information in VAERS reports is not necessarily complete nor is it verified systematically. Reports are classified as serious or nonserious based on regulatory criteria. Reports are coded by VAERS in a uniform way with a limited number of terms using a terminology called COSTART. Coding is useful for search purposes but is necessarily imprecise. VAERS is useful in detecting adverse events related to vaccines and most recently was used for enhanced reporting of adverse events in the national smallpox immunization campaign. VAERS data have always been publicly available. However, it is essential for users of VAERS data to be fully aware of the strengths and weaknesses of the system. VAERS data contain strong biases. Incidence rates and relative risks of specific adverse events cannot be calculated. Statistical significance tests and confidence intervals should be used with great caution and not routinely. Signals detected in VAERS should be subjected to further clinical and descriptive epidemiologic analysis. Confirmation in a controlled study is usually required. An understanding of the system's defined objectives and inherent drawbacks is vital to the effective use of VAERS data in vaccine safety investigations.

Methods of ensuring vaccine safety

With a decreasing disease burden from vaccine-preventable diseases in developed countries, ensuring the safety of vaccines is critically important for maintaining public confidence in vaccination programs and continuing low levels of disease. This will require investment in resources to identify true adverse effects, understand their pathophysiology, and design and manufacture safer vaccines.

Hepatitis B vaccination and the risk of multiple sclerosis

BACKGROUND

Reports of multiple sclerosis developing after hepatitis B vaccination have led to the concern that this vaccine might be a cause of multiple sclerosis in previously healthy subjects.

METHODS

We conducted a nested case-control study in two large cohorts of nurses in the United States, those in the Nurses' Health Study (which has followed 121,700 women since 1976) and those in the Nurses' Health Study II (which has followed 116,671 women since 1989). For each woman with multiple sclerosis, we selected as controls five healthy women and one woman with breast cancer. Information about hepatitis B vaccination was obtained by means of a mailed questionnaire and was confirmed by means of vaccination certificates. The analyses included 192 women with multiple sclerosis and 645 matched controls and were conducted with the use of conditional logistic regression.

RESULTS

The multivariate relative risk of multiple sclerosis associated with exposure to the hepatitis B vaccine at any time before the onset of the disease was 0.9 (95 percent confidence interval, 0.5 to 1.6). The relative risk associated with hepatitis B vaccination within two years before the onset of the disease was 0.7 (95 percent confidence interval, 0.3 to 1.8). The results were similar in analyses restricted to women with multiple sclerosis that began after the introduction of the recombinant hepatitis B vaccine. There was also no association between the number of doses of vaccine received and the risk of multiple sclerosis.

CONCLUSIONS

These results indicate no association between hepatitis B vaccination and the development of multiple sclerosis.

Vaccinations and the risk of relapse in multiple sclerosis. Vaccines in Multiple Sclerosis Study Group

BACKGROUND

There has been some concern that vaccination may precipitate the onset of multiple sclerosis or lead to relapses. Since the recent hepatitis B vaccination program in France, there have been new reports of an increased risk of active multiple sclerosis after vaccination.

METHODS

We conducted a case-crossover study to assess whether vaccinations increase the risk of relapse in multiple sclerosis. The subjects were patients included in the European Database for Multiple Sclerosis who had a relapse between 1993 and 1997. The index relapse was the first relapse confirmed by a visit to a neurologist and preceded by a relapse-free period of at least 12 months. Information on vaccinations was obtained in a standardized telephone interview and confirmed by means of medical records. Exposure to vaccination in the two-month risk period immediately preceding the relapse was compared with that in the four previous two-month control periods for the calculation of relative risks, which were estimated with the use of conditional logistic regression.

RESULTS

Of 643 patients with relapses of multiple sclerosis, 15 percent reported having been vaccinated during the preceding 12 months. The reports of 94 percent of these vaccinations were confirmed. Of all the patients, 2.3 percent had been vaccinated during the preceding two-month risk period as compared with 2.8 to 4.0 percent who were vaccinated during one or more of the four control periods. The relative risk of relapse associated with exposure to any vaccination during the previous two months was 0.71 (95 percent confidence interval, 0.40 to 1.26). There was no increase in the specific risk of relapse associated with tetanus, hepatitis B, or influenza vaccination (range of relative risks, 0.22 to 1.08). Analyses based on risk periods of one and three months yielded similar results.

CONCLUSIONS

Vaccination does not appear to increase the short-term risk of relapse in multiple sclerosis.

Infant immunization with acellular pertussis vaccines in the United States: assessment of the first two years' data from the Vaccine Adverse Event Reporting System (VAERS)

OBJECTIVE

To evaluate the safety of infant immunization with acellular pertussis vaccines in the United States.

BACKGROUND

The US Food and Drug Administration approved the first acellular pertussis vaccine for use in infants in the United States on July 31, 1996.

OUTCOME MEASURES

Adverse events in the United States after infant immunization with pertussis-containing vaccines, representing temporal (but not necessarily causal) associations between vaccinations and adverse events.

DATA SOURCE

Reports to the Vaccine Adverse Event Reporting System (VAERS), a passive national surveillance system.

DESIGN

Reports concerning infant immunization against pertussis between January 1, 1995 (when whole-cell vaccine was in exclusive use) and June 30, 1998 (when acellular vaccine was in predominant use) were analyzed, if the reports were entered into the VAERS database by November 30, 1998.

RESULTS

During the study, there were 285 reports involving death, 971 nonfatal serious reports, and 4514 less serious reports after immunization with any pertussis-containing vaccine. For 1995 there were 2071 reports; in 1996 there were 1894 reports; in 1997 there were 1314 reports, and in the first half of 1998 there were 491 reports. Diphtheria-tetanus-pertussis vaccine (DTP) was cited in 1939 reports, diphtheria-tetanus-whole-cell pertussis-Haemophilus influenzae type b vaccine (DTPH) in 2918 reports, and diphtheria-tetanus-acellular pertussis vaccine (DTaP) in 913 reports. The annual number of deaths during the study was 85 in 1995, 82 in 1996, 77 in 1997, and 41 in the first half of 1998. The annual number of reported events categorized as nonfatal serious (defined as events involving initial hospitalization, prolongation of hospitalization, life-threatening illness, or permanent disability) to VAERS for all pertussis-containing vaccines declined: 334 in 1995, 311 in 1996, 233 in 1997, and 93 in the first half of 1998. Similarly, the annual number of less serious reports to VAERS for pertussis-containing vaccines declined: 1652 in 1995, 1501 in 1996, 1004 in 1997, and 357 in the first half of 1998. A comparison of the adverse event profiles (proportional distributions) for DTaP, DTP, and DTPH, as well as an analysis of specific adverse events considered in a 1991 Institute of Medicine report on the safety of diphtheria-tetanus-pertussis vaccine, did not identify any new, clear safety concerns.

CONCLUSIONS

These findings reflect the administration of millions of doses of acellular pertussis vaccine and are reassuring with regard to the safety of marketed acellular pertussis vaccines. VAERS data, although subject to the limitations of passive surveillance, support the prelicensure data with regard to the safety of the US-licensed acellular pertussis vaccines that we evaluated.

Safety of routine childhood vaccinations. An epidemiological review

Immunisations have been one of the most cost-effective public health interventions in human history. Despite remarkable progress, several challenges face immunisation programs worldwide. Paradoxically, despite vaccines' clear effectiveness in reducing risks of diseases that were previously widely prevalent and caused substantial morbidity and mortality, current vaccination policies have become increasingly controversial due to concerns about vaccine safety. Vaccines, like other pharmaceutical products, are not entirely risk-free. While most known adverse effects are minor and self-limited, some vaccines have been associated with very rare but serious adverse effects. Because such rare effects are often not evident until vaccines come into widespread use, ongoing surveillance programs to monitor vaccine safety are needed. Such monitoring will be essential if the public is to accept the increasing number of new vaccines made possible by biotechnology. The interpretation of data from vaccine safety research is complex and is associated with some uncertainty. Effectively communicating this uncertainty and continuing to improve understanding of rare risks and risk factors are essential for "mature" immunisation programs to maintain public confidence in immunisations.

Unexplained fever in neonates may be associated with hepatitis B vaccine

AIM

To investigate whether hepatitis B vaccination has increased the number of cases of unexplained neonatal fever.

METHOD

The files of all infants born from 1 January 1991 to 31 December 1992, in whom a diagnosis of "injected antibiotic" or "disease of temperature regulation" was recorded, were reviewed. Those who had unexplained fever of 38 degrees C or higher during the first three days of life were divided into two groups: infants who did not receive the hepatitis B vaccine (1991) and infants who did (1992).

RESULTS

In 1992 the incidence of unexplained fever in hepatitis B vaccinated neonates was significantly higher than in the 1991 group of pre-vaccination neonates (35 out of 5819 (0.6%) vs 14 out of 5010 neonates (0.28%) respectively, p=0.013).

CONCLUSIONS

The increase in the number of cases of unexplained neonatal fever seems to be associated with the introduction of routine hepatitis B vaccination on the first day of life. The possibility that an excess number of neonates will undergo unnecessary procedures and treatment to diagnose unexplained fever justifies planning a controlled study to determine whether these preliminary findings point to a significant problem.

Hepatitis B vaccination in hospital personnel and medical students

We determined the prevalence of hepatitis B markers and the compliance to hepatitis B vaccination in a University Hospital of Santa Maria, Lisbon. The program was begun in 1989 for all hospital personnel and students of the medical school. The screening included 2,360 health care workers and 1,153 students; 57% (2,360/4,103) of hospital personnel and 41% (1,153/2,779) of medical students appeared for vaccination. The prevalence of hepatitis B markers was 16.8% (397/2,360) for hospital personnel and 5.5% (64/1,153) for students, the chronic carrier appearing in 0.95% (22/2,360) of hospital personnel and 0.3% (4/1.153) of students. The departments with the highest prevalence were the Biochemical Laboratory (64%, 7/11), Surgery (42%, 13/31), Pulmonary (39%, 9/23), Emergency (29%, 7/24), Hematology Laboratory (29%, 7/24), and Orthopedics (29%, 10/35). The prevalence was higher in students in the last 3 years of medical school than those in the first 3 years (12.2% [22/181] vs. 7.2% [8/110], p = NS). Adverse effects to vaccination occurred in 14.5%, with local pain the most frequent in 8.6%. The serologic efficacy was 95% (1,044/ 1,097). A nonresponse was observed in male workers, 13% (26/200) compared with 5% (45/897) for females (p < 0.05). Older employees also showed higher nonresponse: The average age of workers with anti-HBs of 0 IU/l was 52.3 years and those with anti-HBs of more than 100 IU/l was 38.4 years (p < 0.02). Hepatitis B vaccination is safe and effective. Our study shows the need for a more aggressive approach to the vaccination of health care workers because a significant percentage of them are not protected.

Comparative safety of two recombinant hepatitis B vaccines in children: data from the Vaccine Adverse Event Reporting System (VAERS) and Vaccine Safety Datalink (VSD)

BACKGROUND

Preliminary review of data from the Vaccine Adverse Event Reporting System (VAERS), 1991-1994, revealed that more serious adverse events were reported in children who received a specific brand of recombinant hepatitis B (HepB) vaccine.

OBJECTIVE

To compare the post-marketing safety experience of the two recombinant HepB vaccines licensed for use in infants and children in the United States.

DESIGN

Review of a case series derived from passive surveillance data in the national VAERS. A retrospective cohort study using data from one health maintenance organization participating in Vaccine Safety Datalink (VSD), a computerized record linkage system. POPULATIONS STUDIED: U.S. children, ages birth-10 years for whom adverse events after HepB vaccine were reported to VAERS, 1991-1994. Children, ages birth-6 years, who received HepB vaccine at Kaiser Permanente Medical Care Program, Northern California, 1991-1994.

MAIN OUTCOME MEASURES

VAERS reporting rates for each vaccine by manufacturer were calculated from the numbers of reported events occurring within 30 days of HepB vaccination and the number of doses distributed by the manufacturers. VSD event rates for each vaccine were calculated from the numbers of hospitalization or emergency room visits within 30 days of HepB vaccination and the number of vaccine doses administered to the cohort.

RESULTS

In VAERS, higher rates of serious events (i.e., life threatening or resulting in hospitalization or permanent disability) were reported in children who received Vaccine A vs. Vaccine B (relative risk [RR]: 3.13-8.18, P < 0.01), particularly by those vaccinated in the private (RR: 7.62-28.58, P < 0.01), but not public sector (RR: 2.12, P = 0.19). Similar types of events were reported in recipients of both vaccines. In contrast, analysis of VSD data showed no significant difference in rates of hospitalization or ER visits in children who received either HepB vaccine (RR: 0.96-1.25, P > 0.05).

CONCLUSIONS

Our investigation reveals that it is unlikely there is a true difference between rates of serious events temporally associated with the two HepB vaccines in children. This study demonstrates the dual roles played by VAERS and VSD in providing a more complete picture of the post-marketing safety profile of childhood vaccines, and underscores the importance of using other analytic studies to evaluate findings from passive surveillance systems of adverse events.

Descriptive epidemiology of adverse events after immunization: reports to the Vaccine Adverse Event Reporting System (VAERS), 1991-1994

OBJECTIVE

To provide an overview of the data, function, and performance of the Vaccine Adverse Event Reporting System.

DESIGN

Descriptive and correlational analyses.

SETTING

United States, 1991 through 1994.

SUBJECTS

Reports to the Vaccine Adverse Event Reporting System, a passive national surveillance system, that represents temporal (but not necessarily causal) relationships between vaccinations and adverse events.

MAIN OUTCOME MEASURES

Demographic variables, birth weight, vaccine type, severity of adverse event after immunization.

RESULTS

A total of 38,787 adverse events was reported during the study period without a clearly increasing or decreasing trend in the annual number of total reports or deaths. Of the deaths with known age, 72.4% were reported in the first year of life, and 63.7% of these were male. The peak age for death reports was 1 to 3 months, with a gradual decline through age 9 months, after which death was relatively rare. Adverse events with onset of symptoms the day of vaccination accounted for 45.5% of total reports; 20.4% had onset of symptoms the following day. Onset within 2 weeks after vaccination was noted for 92.5% of all reports. Simultaneous administration of multiple vaccines was noted in 75.7% of reports for immunizations at ages younger than 20 years. In contrast, among those 20 years or older, only 6.0% of reports named multiple vaccines. Wide geographic variations were noted in adverse event reporting rates for children younger than 2 years, and the states with the lowest reporting rates of less serious events included the most populous states.

CONCLUSIONS

The peak age of deaths at ages 1 to 3 months could be expected on the basis of prior studies showing that sudden infant death syndrome deaths peak at that age, that most deaths in the Vaccine Adverse Event Reporting System are attributed to sudden infant death syndrome, and that sudden infant death syndrome has not been associated with vaccination. The large number of reports and national coverage of the Vaccine Adverse Events Reporting System make it useful for monitoring the safety of vaccine lots and for accumulating case series to detect or better understand adverse events that may occur too rarely to be assessed in clinical trials or in the larger studies that are sometimes carried out by manufacturers after vaccine licensure (phase IV studies).