ABSTRACT
Chronic spontaneous urticaria (CSU) involves recurrent, pruritic wheals lasting more than 6 weeks in response to various etiologies, including unknown causality. Though most cutaneous reactions to the COVID-19 vaccine series are self-limited and of short duration, more complex presentations including chronic spontaneous urticaria have been described. To the best of our knowledge, this is the first report of chronic spontaneous urticaria following heterologous mRNA COVID-19 booster vaccination that includes vaccination with both forms of the mRNA vaccine. Our patient received Pfizer-BioNTech for the primary series and Moderna for the booster. After failing several therapies, our patient's urticaria was refractory even to omalizumab. The source for chronic spontaneous urticaria development in our patient may be related to the unique humoral response elicited by receipt of a different mRNA vaccine manufacturer.
Subject(s)
COVID-19 Vaccines , Chronic Urticaria , Immunization, Secondary , Humans , COVID-19 Vaccines/adverse effects , Immunization, Secondary/adverse effects , BNT162 Vaccine/adverse effects , Female , Omalizumab/therapeutic use , COVID-19/prevention & control , COVID-19/complications , Middle Aged , Male , AdultABSTRACT
The first dose of COVID-19 vaccines led to an overall reduction in cardiovascular events, and in rare cases, cardiovascular complications. There is less information about the effect of second and booster doses on cardiovascular diseases. Using longitudinal health records from 45.7 million adults in England between December 2020 and January 2022, our study compared the incidence of thrombotic and cardiovascular complications up to 26 weeks after first, second and booster doses of brands and combinations of COVID-19 vaccines used during the UK vaccination program with the incidence before or without the corresponding vaccination. The incidence of common arterial thrombotic events (mainly acute myocardial infarction and ischaemic stroke) was generally lower after each vaccine dose, brand and combination. Similarly, the incidence of common venous thrombotic events, (mainly pulmonary embolism and lower limb deep venous thrombosis) was lower after vaccination. There was a higher incidence of previously reported rare harms after vaccination: vaccine-induced thrombotic thrombocytopenia after first ChAdOx1 vaccination, and myocarditis and pericarditis after first, second and transiently after booster mRNA vaccination (BNT-162b2 and mRNA-1273). These findings support the wide uptake of future COVID-19 vaccination programs.
Subject(s)
COVID-19 Vaccines , COVID-19 , Cardiovascular Diseases , Vaccination , Adult , Aged , Female , Humans , Male , Middle Aged , 2019-nCoV Vaccine mRNA-1273/administration & dosage , 2019-nCoV Vaccine mRNA-1273/adverse effects , BNT162 Vaccine/adverse effects , BNT162 Vaccine/administration & dosage , Cardiovascular Diseases/epidemiology , ChAdOx1 nCoV-19/administration & dosage , ChAdOx1 nCoV-19/adverse effects , Cohort Studies , COVID-19/prevention & control , COVID-19 Vaccines/adverse effects , COVID-19 Vaccines/administration & dosage , England/epidemiology , Immunization, Secondary/adverse effects , Incidence , Myocardial Infarction/epidemiology , Myocardial Infarction/etiology , Myocarditis/epidemiology , Myocarditis/etiology , Pulmonary Embolism/epidemiology , Pulmonary Embolism/etiology , Thrombosis/epidemiology , Thrombosis/etiology , Vaccination/adverse effects , Adolescent , Young Adult , Aged, 80 and overABSTRACT
INTRODUCTION: Different COVID-19 vaccines are being utilized as boosters. This systematic review and meta-analysis aims to evaluate the reactogenicity of COVID-19 vaccines given as booster doses, according to vaccine type, dose, timing, participant characteristics and primary immunization regimen received. METHODS: Four databases (MEDLINE, Embase, Web of Science and CENTRAL) were searched for randomized controlled trials between 1 January 2020 and 1 January 2023 according to predetermined criteria. RESULTS: Twenty-eight studies describing 19 vaccines of four different types (viral vector, inactivated, mRNA and protein sub-unit) were identified. BNT162b2 vaccine (Pfizer-BioNTech) was selected as the control as it was most often compared with other vaccines. Fever, fatigue, headache, injection-site pain, redness, and swelling were the most frequently reported solicited events. mRNA vaccines were the most reactogenic, followed by viral vector vaccines and protein sub-unit vaccines, while inactivated vaccines were the least reactogenic. Full-dose vaccines were more reactogenic than half-dose vaccines. Heterologous BNT162b2 boosters were more reactogenic than boosters with the same vaccine used for primary immunization. CONCLUSIONS: COVID-19 vaccine booster schedules have distinct reactogenicity profiles, dependent on dose and vaccine type, which may allow targeted recommendations and provide choice for specific populations. Greater standardization of adverse event reporting will aid future studies.
Subject(s)
COVID-19 Vaccines , COVID-19 , Immunization, Secondary , Humans , BNT162 Vaccine/adverse effects , COVID-19/prevention & control , COVID-19 Vaccines/adverse effects , Immunization, Secondary/adverse effectsABSTRACT
BACKGROUND AND AIMS: The SARS-CoV-2 mRNA vaccines are associated with an increased risk of myocarditis. This association appears to be strongest in male adolescents and younger males and after the second dose. The aim was to evaluate the risk of myocarditis following SARS-CoV-2 mRNA booster vaccination in 12-to-39-year-olds. METHODS: A multinational cohort study was conducted using nationwide register data in Denmark, Finland, Norway, and Sweden and comprising all 8.9 million individuals residing in each of the four countries. Participants were followed for an inpatient diagnosis of myocarditis. In each of the four countries, Poisson regression was used to estimate adjusted incidence rate ratios (IRRs) of myocarditis comparing vaccination schedules, with associated 95% confidence intervals (CIs). Country-specific results were combined in meta-analyses. RESULTS: A total of 8.9 million residents were followed for 12 271 861 person-years and 1533 cases of myocarditis were identified. In 12-to-39-year-old males, the 28-day acute risk period following the third dose of BNT162b2 or mRNA-1273 was associated with an increased incidence rate of myocarditis compared to the post-acute risk period 28 days or more after the second dose [IRR 2.08 (95% CI 1.31-3.33) and 8.89 (2.26-35.03), respectively]. For females, the corresponding IRR was only estimable for BNT162b2, 3.99 (0.41-38.64). The corresponding absolute risks following the third dose of BNT162b2 and mRNA-1273 in males were 0.86 (95% CI 0.53-1.32) and 1.95 (0.53-4.99) myocarditis events within 28 days per 100 000 individuals vaccinated, respectively. In females, the corresponding absolute risks following the third dose of BNT162b2 were 0.15 (0.04-0.39) events per 100 000 individuals vaccinated. No deaths occurred within 30 days of vaccine-related cases. CONCLUSIONS: The results suggest that a booster dose is associated with increased myocarditis risk in adolescents and young adults. However, the absolute risk of myocarditis following booster vaccination is low.
Subject(s)
COVID-19 Vaccines , COVID-19 , Myocarditis , Adolescent , Adult , Child , Female , Humans , Male , Young Adult , 2019-nCoV Vaccine mRNA-1273 , BNT162 Vaccine , Cohort Studies , COVID-19/epidemiology , COVID-19/prevention & control , COVID-19 Vaccines/adverse effects , Myocarditis/chemically induced , Myocarditis/epidemiology , Vaccination/adverse effects , Immunization, Secondary/adverse effectsABSTRACT
BACKGROUND: Primary and booster vaccinations are critical for mitigating COVID-19 transmission, morbidity, and mortality. Future booster vaccine campaigns rely on an increased understanding of vaccine hesitancy. OBJECTIVE: To evaluate self-reported allergic and skin vaccine reactions as factors potentially associated with vaccine hesitancy in a nationwide vaccine allergy registry. METHODS: Responses to survey questions concerning COVID-19 vaccine perceptions, coded from free text by 2 independent reviewers. Multivariable logistic regression models were used to determine the association between changed negative perception and respondent demographics, vaccination history, and reaction characteristics. RESULTS: A total of 993 individuals (median of 46 years [IQR, 36-59], 88% female, 82% White) self-reported reactions to COVID-19 vaccination. Reactions included the following: delayed large local skin reaction (40%), hives/urticaria (32%), immediate large local skin reaction (3%), swelling (3%), anaphylaxis (2%), and other or unspecified (20%). Most respondents were initially unconcerned about the safety of COVID-19 vaccines (56%). After reactions, 401 of 993 (40%) report negative change in perception of vaccination, with more than half of these respondents (n = 211, 53%) citing their reasoning as a negative experience with adverse effects. Of 102 individuals asked about future vaccination, 79 (77%) indicated that they were unlikely or very unlikely to receive future COVID-19 vaccinations. Increased negative perception after reaction was associated with younger age, later COVID-19 vaccination dose number, and reaction type. CONCLUSION: Our findings reveal that an individual's experience with allergic or cutaneous adverse effects after COVID-19 vaccination affects attitudes and decision-making regarding future vaccination, even in initially non-hesitant individuals. Further investigation of secondary vaccine hesitancy is necessary for adapting public health messaging to this important population.
Subject(s)
COVID-19 Vaccines , COVID-19 , SARS-CoV-2 , Vaccination Hesitancy , Humans , Female , Male , COVID-19 Vaccines/adverse effects , Middle Aged , Adult , Vaccination Hesitancy/psychology , COVID-19/prevention & control , COVID-19/psychology , SARS-CoV-2/immunology , Surveys and Questionnaires , Immunization, Secondary/adverse effects , Vaccination/adverse effects , Vaccination/psychology , Self Report , Hypersensitivity/psychologyABSTRACT
BACKGROUND: COVID-19 vaccines have been recommended to people with multiple sclerosis (pwMS) and, to ensure durable immunity, a third booster dose has been administered in several countries. Data about potential risks associated with the third booster dose in pwMS, such as vaccine-triggered disease exacerbations, are still scarce. OBJECTIVE: To investigate whether the administration of a third booster dose of mRNA COVID-19 vaccines was associated with an increased risk of short-term disease reactivation in a large cohort of pwMS. METHODS: We retrospectively selected 1265 pwMS who received a third booster dose of an mRNA COVID-19 vaccine. Demographic and clinical data were collected, including the presence, number and characteristics of relapses in the 60 days prior to and after the third booster dose. RESULTS: In the selected cohort, the relapse rate in the two months after administration of the third booster dose of mRNA COVID-19 vaccines did not increase when compared with the prior two months. Indeed, the percentage of pwMS experiencing relapses in the 60 days following the administration of the third booster dose was 2.1%, similar to the percentage recorded in 60 days prior to vaccination, which was 1.9%. CONCLUSIONS: The third booster dose of mRNA COVID-19 vaccines appeared to be safe for pwMS.
Subject(s)
COVID-19 Vaccines , COVID-19 , Multiple Sclerosis , Humans , Antibodies, Viral , Chronic Disease , COVID-19/prevention & control , COVID-19 Vaccines/adverse effects , Multiple Sclerosis/complications , Recurrence , Retrospective Studies , Vaccination/adverse effects , Immunization, Secondary/adverse effects , mRNA Vaccines/adverse effectsABSTRACT
This study assessed the association between COVID-19 vaccines, SARS-CoV-2 infection and the risk of thrombocytopenia and venous thromboembolism (VTE). This self-controlled case series study used hospital records between 1st February 2021 and 28th February 2022 linked to the national immunisation registry and COVID-19 surveillance data in Malaysia. Conditional Poisson regression was used to estimate incidence rate ratios (IRR) of events in the risk period (day 1-21 post-exposure) relative to control period with the corresponding 95% confidence interval (CI) adjusted for calendar period. We found no significant increased risk of thrombocytopenia in 1-21 days following BNT162b2, CoronaVac and ChAdOx1 vaccines while the risk was increased following SARS-CoV-2 infection (IRR 15.52, 95% CI 13.38-18.00). Similarly, vaccination with BNT162b2, CoronaVac, or ChAdOx1 was not associated with an increased risk of VTE during the 1-21 days risk period. SARS-CoV-2 infection was associated with increased risk of VTE (IRR 39.84, 95% CI 27.45-32.44). Our findings showed low event rates of thrombocytopenia and VTE following booster vaccination with comparable safety profiles between those who received homologous and heterologous booster combinations. Our findings showed the risk of thrombocytopenia and VTE was not increased after COVID-19 vaccination while the risks were substantially higher after SARS-CoV-2 infection.
Subject(s)
COVID-19 Vaccines , COVID-19 , Thrombocytopenia , Venous Thromboembolism , Humans , BNT162 Vaccine , COVID-19/epidemiology , COVID-19/prevention & control , COVID-19 Vaccines/adverse effects , Research Design , SARS-CoV-2 , Thrombocytopenia/chemically induced , Thrombocytopenia/epidemiology , Vaccination/adverse effects , Venous Thromboembolism/chemically induced , Venous Thromboembolism/epidemiology , Malaysia , Immunization, Secondary/adverse effectsABSTRACT
BCG vaccination and revaccination are increasingly being considered for the protection of adolescents and adults against tuberculosis and, more broadly, for the off-target protective immunological effects against other infectious and noninfectious diseases. Within an international randomized controlled trial of BCG vaccination in healthcare workers (the BRACE trial), we evaluated the incidence of local and serious adverse events, as well as the impact of previous BCG vaccination on local injection site reactions (BCG revaccination). Prospectively collected data from 99% (5351/5393) of participants in Australia, Brazil, Spain, The Netherlands and the UK was available for analysis. Most BCG recipients experienced the expected self-limiting local injection site reactions (pain, tenderness, erythema, swelling). BCG injection site itch was an additional common initial local symptom reported in 49% of BCG recipients. Compared to BCG vaccination in BCG-naïve individuals, BCG revaccination was associated with increased frequency of mild injection site reactions, as well as earlier onset and shorter duration of erythema and swelling, which were generally self-limiting. Injection site abscess and regional lymphadenopathy were the most common adverse events and had a benign course. Self-resolution occurred within a month in 80% of abscess cases and 100% of lymphadenopathy cases. At a time when BCG is being increasingly considered for its off-target effects, our findings indicate that BCG vaccination and revaccination have an acceptable safety profile in adults.
Subject(s)
Abscess , BCG Vaccine , Adolescent , Adult , Humans , BCG Vaccine/adverse effects , Health Personnel , Immunization, Secondary/adverse effects , Injection Site Reaction/epidemiology , Vaccination/adverse effectsABSTRACT
INTRODUCTION: The rapid roll-out of novel COVID-19 vaccines made near real-time post-marketing safety surveillance essential to identify rare and long-term adverse events following immunization (AEFIs). In light of the ongoing booster vaccination campaigns, it is key to monitor changes in observed safety patterns post-vaccination. The effect of sequential COVID-19 vaccinations, as well as heterologous vaccination sequences, on the observed post-vaccination safety pattern, remains largely unknown. METHODS: The primary objective of this study was to describe the profile of spontaneously reported AEFIs following COVID-19 vaccination in the Netherlands, including the primary and booster series. Reports from consumers and healthcare professionals were collected via a COVID-19 vaccine-tailored online reporting form by the National Pharmacovigilance Centre Lareb (Lareb) between 6 January 2021 and 31 August 2022. The data were used to describe the most frequently reported AEFIs per vaccination moment, the consumer experienced burden per AEFI, and differences in AEFIs reported for homologous and heterologous vaccination sequences. RESULTS: Lareb received 227,884 spontaneous reports over a period of twenty months. Overall, a high degree of similarity in local and systemic AEFIs per vaccination moment was observed, with no apparent change in the number of reports of serious adverse events after multiple COVID-19 vaccinations. No differences in the pattern of reported AEFIs per vaccination sequence was observed. CONCLUSION: Spontaneous reported AEFIs demonstrated a similar reporting pattern for homologous and heterologous primary and booster series of COVID-19 vaccination in the Netherlands.
Subject(s)
COVID-19 Vaccines , COVID-19 , Humans , COVID-19 Vaccines/adverse effects , Adverse Drug Reaction Reporting Systems , Netherlands/epidemiology , Immunization, Secondary/adverse effects , COVID-19/prevention & control , Vaccination/adverse effectsABSTRACT
BACKGROUND: Chemotherapy and hematopoietic stem cell transplantation (HSCT) can damage the immune system, and may result in a loss of protection from infectious diseases. This study aimed to evaluate the impact of these treatments on the decrease in antibody titers of the measles, mumps, and rubella (MMR) vaccine and seroconversion post-revaccination of MMR. METHODS: After completion of treatment for primary diseases, participants received an MMR revaccination. Antibody titers for MMR before revaccination were analyzed for all 110 children. After revaccination, 68 participants received a follow-up evaluation of antibody titer and adverse reaction. RESULTS: Multivariable analysis showed that therapeutic schedules were the only factor correlated with lack of antibody titers for measles after completing treatment (P = 0.008), while for mumps and rubella, no statistically significant difference was observed. Importantly, our study clearly demonstrated positive seroconversion rates for measles (97.5%), mumps (81.0%), and rubella (93.2%), with antibody levels rising across the board and peaking at around 6 months following revaccination. However, 6 months after revaccination, a downtrend of antibody titer levels was observed, which is comparatively earlier than the waning immunity observed in healthy children. Furthermore, we found MMR revaccination to be safe, with only a single adverse reaction (local pain at the injection site) reported. CONCLUSIONS: MMR revaccination is immunogenic for the population. We suggest periodic monitoring of antibody titers, in addition to a booster vaccination, although the optimal timing of booster vaccination remains to be investigated further.
Subject(s)
Hematopoietic Stem Cell Transplantation , Measles-Mumps-Rubella Vaccine , Measles , Mumps , Rubella , Child , Humans , Infant , Hematopoietic Stem Cell Transplantation/adverse effects , Immunization, Secondary/adverse effects , Measles/prevention & control , Measles-Mumps-Rubella Vaccine/administration & dosage , Mumps/prevention & control , Prospective Studies , Rubella/prevention & control , Chemotherapy, Adjuvant/adverse effectsSubject(s)
COVID-19 Vaccines , Cardiovascular Diseases , Immunization, Secondary , Vaccines, Combined , Humans , Cardiovascular Diseases/chemically induced , Cardiovascular Diseases/diagnostic imaging , Cardiovascular Diseases/etiology , COVID-19/prevention & control , COVID-19 Vaccines/adverse effects , COVID-19 Vaccines/therapeutic use , Immunization, Secondary/adverse effects , Myocardial Infarction/chemically induced , Myocardial Infarction/etiology , Pulmonary Embolism/chemically induced , Pulmonary Embolism/diagnostic imaging , Pulmonary Embolism/etiology , Stroke/chemically induced , Stroke/etiology , Vaccines, Combined/adverse effects , Vaccines, Combined/therapeutic useSubject(s)
COVID-19 Vaccines , COVID-19 , Immunization, Secondary , Kidney Failure, Chronic , Renal Dialysis , Vaccines, Combined , Humans , Immunization, Secondary/adverse effects , Immunization, Secondary/methods , Kidney Failure, Chronic/complications , Kidney Failure, Chronic/immunology , Kidney Failure, Chronic/therapy , Vaccines, Combined/immunology , Vaccines, Combined/therapeutic use , COVID-19 Vaccines/immunology , COVID-19 Vaccines/therapeutic use , Immunogenicity, Vaccine/immunology , COVID-19/complications , COVID-19/immunology , COVID-19/prevention & controlABSTRACT
With benefits unclear, some scientists question new round of shots for young people.
Subject(s)
COVID-19 Vaccines , COVID-19 , Immunization, Secondary , Myocarditis , Adolescent , Humans , COVID-19/prevention & control , Immunization, Secondary/adverse effects , Young Adult , Adult , Myocarditis/epidemiology , Myocarditis/etiology , United StatesABSTRACT
Importance: COVID-19 vaccine boosters or third doses are recommended for adolescents and adults who completed their initial COVID-19 vaccine course more than 5 months prior. Minimal data are available on COVID-19 vaccine booster or third dose reactogenicity among pregnant and lactating individuals. Objective: To describe the reactions to the booster or third dose of the COVID-19 vaccine and vaccine experiences among pregnant and lactating individuals. Design, Setting, and Participants: Beginning in October 2021, a follow-up Research Electronic Data Capture (REDCap) survey regarding a COVID-19 vaccine booster or third dose was sent to 17â¯504 participants in an ongoing online prospective cohort study on COVID-19 vaccines among pregnant and lactating individuals. A convenience sample of adults enrolled in the online prospective study who were pregnant, lactating, or neither pregnant nor lactating at the time of their booster or third dose was eligible for this follow-up survey; 17â¯014 (97.2%) completed the follow-up survey. Exposure: Receipt of a booster or third dose of the COVID-19 vaccine. Main Outcomes and Measures: Self-reported vaccine reactions less than 24 hours after the dose. Results: As of April 4, 2022, 17â¯014 eligible participants (mean [SD] age, 33.3 [3.5] years) responded to the booster or third dose survey; of these, 2009 (11.8%) were pregnant at the time of their booster or third dose, 10â¯279 (60.4%) were lactating, and 4726 (27.8%) were neither pregnant nor lactating. After a COVID-19 booster or third dose, most individuals (14â¯074 of 17â¯005 [82.8%]) reported a local reaction, and 11â¯542 of 17â¯005 (67.9%) reported at least 1 systemic symptom. Compared with individuals who were neither pregnant nor lactating, pregnant participants were more likely to report any local reaction to a COVID-19 booster or third dose (adjusted odds ratio [aOR], 1.2; 95% CI, 1.0-1.4; P = .01) but less likely to report any systemic reaction (aOR, 0.7; 95% CI, 0.6-0.8; P < .001). Most pregnant (1961 of 2009 [97.6%]) and lactating (9866 of 10â¯277 [96.0%]) individuals reported no obstetric or lactation concerns after vaccination. Conclusions and Relevance: This study suggests that COVID-19 vaccine boosters or third doses were well tolerated among pregnant and lactating individuals. Data to evaluate tolerability of boosters or additional doses among pregnant and lactating individuals will be important as they are considered for these populations.
Subject(s)
COVID-19 Vaccines , COVID-19 , Pregnancy Complications, Infectious , Vaccines , Adolescent , Adult , COVID-19/epidemiology , COVID-19/prevention & control , COVID-19 Vaccines/adverse effects , Female , Humans , Immunization, Secondary/adverse effects , Lactation , Pregnancy , Pregnancy Complications, Infectious/prevention & control , Prospective StudiesABSTRACT
BACKGROUND: To meet the demand for effective and affordable inactivated polio vaccines (IPVs), a reduced dose, aluminium hydroxide (Al(OH)3)-adjuvanted IPV vaccine was developed (IPV-Al, Picovax®) and evaluated in clinical trials. The present trial is an extension of two previous trials (a primary and a booster trial). The aim was to evaluate the persistence of seroprotective antibodies (poliovirus type-specific antibody titre ≥ 8) in 4-year-old children who previously received IPV-Al as primary and booster vaccine doses and to determine the potential booster response and safety profile of an additional dose of IPV-Al. METHODS: Children participating in the two previous trials were invited to receive one additional dose of IPV-Al at 4 years of age (2.5 years after the booster dose) and to have their blood samples collected to measure the pre- and post-vaccination antibody titres. Systemic adverse events (AEs) and local reactogenicity were recorded. RESULTS: At study entry, the seroprotection rates were 89.2%, 100% and 91.1% against poliovirus type 1, 2 and 3, respectively. The additional vaccination with IPV-Al boosted the level of poliovirus type 1, 2 and 3 antibodies to above the seroprotection threshold for all but one subject, i.e., 99.4% for type 1 and 100% for types 2 and 3. The additional dose induced a robust booster response of a 26.3-, 13.9- and 30.9-fold increase in titre for poliovirus types 1, 2 and 3, respectively. The vaccine was well tolerated, with only mild and transient AEs reported. CONCLUSIONS: The present trial demonstrated that the primary vaccination with an aluminium-adjuvanted reduced dose IPV induced a persistent immune memory as evidenced by the robust anamnestic response when the subjects were re-exposed to the antigen 2.5 years after the last dose. Thus, the IPV-Al is an efficient and safe addition to increase the availability of inactivated polio vaccines globally. (ClinicalTrials.gov reg no. NCT04448132).
Subject(s)
Poliomyelitis , Poliovirus , Adjuvants, Immunologic , Aluminum , Antibodies, Viral , Child, Preschool , Humans , Immunization, Secondary/adverse effects , Infant , Poliomyelitis/etiology , Poliomyelitis/prevention & control , Poliovirus Vaccine, InactivatedABSTRACT
OBJECTIVES: To estimate the risk of recurrence of adverse events following immunization (AEFIs) upon revaccination and to determine among patients with suspected vaccine allergy whether allergy skin test positivity was associated with AEFI recurrence. STUDY DESIGN: This prospective observational study included patients assessed in the Canadian Special Immunization Clinic Network from 2013 to 2019 with AEFIs who required revaccination with the vaccine temporally associated with their AEFI. Participants underwent standardized assessment and data collection. Special Immunization Clinic physicians used guidelines to inform their recommendations. Participants were followed up after revaccination to capture AEFI recurrences. Data were transferred to a central database for descriptive analysis. RESULTS: Overall, 588 participants were assessed for 627 AEFIs; 570 (91%) AEFIs occurred in children <18 years of age. AEFIs included immediate hypersensitivity (130/627; 21%), large local reactions (110/627; 18%), nonurticarial rash (51/627; 8%), seizures (26/627; 4%), and thrombocytopenia (11/627; 2%). Revaccination was recommended to 513 of 588 (87%) participants. Among participants recommended and due for revaccination during the study period, 63% (299/477) were revaccinated. AEFI recurrence was 10% (31/299) overall, 31% (15/49) for large local reactions, and 7% (5/66) for immediate hypersensitivity. No recurrence was serious. Among 92 participants with suspected vaccine allergy who underwent skin testing and were revaccinated, the negative predictive value of skin testing for AEFI recurrence was 96% (95% CI 92.5%-99.5%). CONCLUSIONS: Most individuals with AEFIs were safely revaccinated. Among those with suspected vaccine allergy, skin testing may help determine the safety of revaccination.