Adverse Events Following Immunization Research Articles

Arthritis as an adverse event of special interest post COVID-19 vaccine implementation

COVID-19 vaccines are currently in development or being rolled out as a public health response to manage the pandemic. While vaccines selected for mass public immunization programs would have demonstrated safety and efficacy in Phase 3 trials, vaccine safety monitoring including reporting of adverse events following immunization (AEFI) and investigation of reported cases are still required for safety surveillance. Monitoring of AEFI post COVID-19 vaccination is quite relevant to clinicians.

Possible Causes of and Measures to Minimise Risks of Abscesses Following DTP Vaccination

Registration and analysis of adverse events following immunisation (AEFIs) allow for objective assessment and systematisation of AEFI causes, and promotion of vaccination safety. Development of abscesses after DTP vaccination is a fairly common AEFI, however, they are not included in the “Side effects” part of the patient information leaflet of the vaccine. The aim of the study was to analyse reasons for abscess development after DTP vaccination and to elaborate recommendations on enhancing the vaccine safety. The review of literature data, solicited reports on AEFIs, and AEFI investigation reports submitted to the Scientific Centre for Expert Evaluation of Medicinal Products during 2014–2018 suggests that abscesses associated with DTP vaccination may be caused by the vaccine reactogenicity, quality defects arising during production or distribution, and vaccine administration errors by healthcare personnel. Lack of information in the documents submitted by medical institutions does not allow to rule out any of the identified reasons. The minimisation of risks of abscesses requires quality control of DTP vaccines, maintenance of the cold chain during transportation and storage, and compliance with aseptic regulations during administration. Additional pharmacovigilance measures will also help enhance vaccination safety: improvement and standardisation of data collection during investigation of abscess development in the post-vaccination period, obligatory inclusion of data on the thickness of children’s subcutaneous adipose tissue (weight, body mass index) and the length of the needle used for vaccination in AEFI investigation reports. It is advisable to add information on abscess risk in the “Side effects” part of the patient information leaflet of the DTP vaccine, and to update the “Dosage regimen and administration route” and “Precautions” parts in order to minimise the risk. Personnel of healthcare facilities performing vaccination should be made aware of the importance of providing detailed data on AEFIs for subsequent objective analysis.

Adverse events following immunization: Findings from 2017/2018 measles vaccination campaign, Nigeria AEFI reporting in 2017/2018 measles vaccination campaign

IntroductionAn Adverse event following immunization (AEFI) is an untoward medical occurrence following immunization and which may not have a necessary causal relationship with the usage of a vaccine. The World Health Organization categories AEFI into two; serious and non-serious. An AEFI is considered serious if it is life-threatening, requires inpatient hospitalization or results in death. The measles vaccine is safe and effective however because it is a live-attenuated injectable vaccine it is more prone to AEFI as compared to non-injectable vaccines when given in large numbers over a short period as is the nature of measles mass vaccination campaigns (MVC). This article describes Nigeria’s experience on AEFI reporting during the 2017/2018 Measles vaccination campaign (MVC). MethodsWe reviewed various materials which included the Open Data Kit (ODK) which is an open source smartphone-based data collecting tool, operations room reports, measles campaign tally sheets, AEFI line listing forms, the post measles campaign coverage survey report and the report of the AEFI national expert committee review of the 2017/2018 Nigeria measles MVC. ResultsA total of 6,214 suspected cases of AEFI were line listed from all 36 states and the Federal Capital Territory(FCT) during the 2017/2018 MVC with Fever(38%) and pain at injection site the (30%)most common reports. Overall, 99.7% AEFIs were reported to be non-serious AEFIs, with almost all cases resolved fully with no long-term sequalae.. The national incidence of suspected AEFI per 100,000 population was 16.3 with subnational incidence highest in Kebbi state (101.3/100,000) and lowest in Bayelsa state (0.8/100,000). ConclusionAdequate AEFI reporting, Investigation and management remains important in managing the risk of a disruption of mass campaigns. The deployment of supervisors during campaign may play an important role in improving the identification and reporting of suspected AEFI. Further inquiries about AEFIs during the post campaign coverage evaluation also played a role in improving AEFI reporting and documentation. The real-time, on the spot, follow up by the national operations team helped with decision making and intervention including AEFI investigations and assessments.

Safety of live attenuated herpes zoster vaccine in Australian adults 70–79 years of age: an observational study using active surveillance

ObjectivesTo assess the safety of live attenuated herpes zoster vaccine live (ZVL) through cumulative analysis of near real-time, participant-based active surveillance from Australia’s AusVaxSafety system.Design and settingZVL was funded in...

A DESCRIPTIVE STUDY ON CLASSIFICATION OF ADVERSE EVENTS FOLLOWING IMMUNIZATION AMONG INFANTS ATTENDING MATERNALAND CHILD HEALTH HOSPITAL, BANGALORE

Background: Vaccination is a vital component of the public health programs and among most cost effective medical intervention. Vaccines are usually safe and effective. However, like any other pharmaceutical products, adverse events may occur occasionally following vaccination. Hence, the present study was conducted with objective to assess proportion of AEFI and classify them based on severity as minor, severe and serious and based on site as local and systemic reactions. Material and Methods:Aone year, prospective, vaccine safety study was undertaken in maternal and child health hospital, Bangalore among mothers who delivered during the study period. A total of 110 infants were enrolled in the study and were followed for 1 year. Telephone survey of all mothers was conducted and all AEFI were recorded. Results: Out of 110 infants, 96 (87.3%) of study subjects had one or more AEFI for primary immunization. Minor reactions like pain, swelling and redness were 42% which are local reactions and fever accounted for 54.3% of all reported AEFI which is systemic reaction. Conclusion:The adverse events reported were mild and non-serious. Majority of the infants had only minor reactions which completely resolved with or without treatment. All were solicited reactions. Hence the vaccines given under UIPwere safe among infants.

Attitude towards childhood vaccination among parents in a rural area of Trivandrum district

Background: Vaccines are simple and widely accepted as one of the most important medical strategy of modern world in the prevention of morbidity and mortality. In order to ensure the protective benefits of vaccines, it is essential that the vaccine coverage should reach between 80-100% of a population, with required coverage dependent on the concerned vaccine and the illness that it is designed to prevent. Vaccine hesitancy is defined as the reluctance to be vaccinated or have one's children vaccinated. In this study, we assess the attitude of parents towards childhood vaccinations and the prevalence of vaccine hesitancy among parents in a rural area in Thiruvananthapuram district.Methods: A cross-sectional study was carried out among parents of children below the age of 15 years, who are residents of a rural area in Thiruvananthapuram district. Data was collected using the parents’ attitude about childhood vaccination (PACV) survey, with the consent of the participants. The collected data entered into MS Excel and analysis was carried out using SPSS 20.Results: Out of 100 participating parents, 14 (14%) parents were concerned about the adverse events following immunization (AEFI). At the same time, the maximum score obtained on the PACV scale was just 24 out of 100. Further, vaccine hesitancy among the parents was found to be only 2 (2%).Conclusions: There is good vaccine acceptance among the parents residing in a rural area, even though many are from low socio-economic status.

Reasons of the delayed vaccination, recommendations and safety of vaccination in children with congenital heart disease in Zhejiang, China

ABSTRACT There has been a considerable controversy about vaccination practices in Children with congenital heart disease (CHD) in China. This study aims to identify the reasons for deferring vaccination among the patient population attending the Vaccination Consultation Clinic in Zhejiang Province and the safety of their vaccination. We analyzed the data of 2442 children with CHD, who visited to our clinic from January 2016 to March 2019. A questionnaire survey was conducted to investigate the reasons for their delayed vaccination. Information about the following vaccination and Adverse Events Following Immunization (AEFI) was collected. Most of the enrolled children did not receive vaccines on time before consultation. The reasons for their deferring vaccination included: 1. Providers in the community health center refused to administer vaccines (77.6%); 2. Parents’ concerns about the safety of vaccines (19.0%); 3. Parents’ doubts about the efficiency of vaccines after certain drug applications (3.4%). According to the evaluation reports issued by the Vaccination Consultation Clinic, 83.7% of CHD children were recommended to be vaccinated on the nationally recommended schedule, 14.4% were recommended to defer some specific vaccination, and 1.9% were recommended to defer all vaccination. Among the group who received vaccines on nationally recommended schedule, the AEFI rate was 33.5/100 000. No rare or serious rare vaccine reactions were observed. Our study provides evidence that routine vaccination is safe in the majority of this patient population.

Review of near real-time vaccine safety surveillance

Post-marketing vaccine safety surveillance, including both passive and active surveillances, aims to detect and alert to signals of adverse events following immunization (AEFI), and to further ensure public safety and public confidence in vaccination. Active surveillance could proactively seek information of AEFI and timely investigate the potential safety signals, therefore, it has become the main development trend of post-marketing surveillance worldwide. Nowadays, there is an ongoing interest in developing active surveillance systems that can incorporate and use existing electronic data such as administrative claims and electronic health records. Researchers have also began exploring ways of accruing data closer to "real-time" in order to speed the recognition of potential safety problems.This near real-time vaccine safety surveillance is gradually emerging worldwide. This study reviews the development and methodology of near real-time surveillance and aims to accelerate the foundation of the active surveillance system for vaccine safety in China.

Inclusion of Safety-Related Issues in Economic Evaluations for Seasonal Influenza Vaccines: A Systematic Review.

(1) Background: Vaccines for seasonal influenza are a good preventive and cost-effective strategy. However, it is unknown if and how these economic evaluations include the adverse events following immunization (AEFI), and what the impact of such inclusion is on the health economic outcomes. (2) Methods: We searched the literature, up to January 2020, to identify economic evaluations of seasonal influenza vaccines that considered AEFIs. The review protocol was published in PROSPERO (CDR42017058523). (3) Results: A total of 52 economic evaluations considered AEFI-related parameters in their analyses, reflecting 16% of the economic evaluations on seasonal influenza vaccines in the initial study selection. Most studies used the societal perspective (64%) and evaluated vaccination of children (37%). Where considered, studies included direct medical costs of AEFIs (90%), indirect costs (27%), and disutilities/quality-adjusted life years loss due to AEFIs (37%). The majority of these studies accounted for the effects of the costs of AEFI on cost-effectiveness for Guillain–Barré syndrome. In those papers allowing cost share estimation, direct medical cost of AFEIs was less than 2% of total direct costs. (4) Conclusions: Although the overall impact of AEFIs on the cost-effectiveness outcomes was found to be low, we urge their inclusion in economic evaluations of seasonal influenza vaccines to reflect comprehensive reports for the decision makers and end-users of the vaccination strategies.

Post-marketing safety surveillance for inactivated Enterovirus 71 vaccines in Jiangsu, China from 2017 to 2019

IntroductionTwo types of enterovirus 71 (EV71) vaccines, manufactured using human diploid (H2) and Vero cells, have been administered in Jiangsu Province, China since 2017. In this study, we evaluated their safety profiles using records collected from the Chinese National Adverse Events Following Immunization (AEFIs) Information System (CNAEFIS) and Electronic Immunization Registries System (EIRS) between 2017 and 2019. MethodsDemographic characteristics of the patients, AEFI incidence rates(IRs), symptoms, and time intervals were summarized from the reported AEFI data in the CNAEFIS. Also, the administered doses of the two vaccines were exported from the EIRS to calculate the IRs of AEFIs and thus compare the AEFIs between the two types of EV71 vaccines. ResultsIn total, 209, 407, and 344 AEFIs cases following EV71 vaccine administration were reported during 2017, 2018, and 2019, respectively, yielding IRs of 59.2, 48.2, and 54.2 per 100,000 doses, respectively. Fever, irritability, allergic eruptions, fatigue, loss of appetite, redness and induration at the injection site were the most commonly reported AEFIs. No significant differences in rare reactions were found between the two types of EV71 vaccinations. The majority of AEFIs were developed within 30 min to 3 days after administration. ConclusionEV71 vaccines showed satisfactory safety profiles since their first use 3 years ago in the Jiangsu Province. The AEFI profiles were identical to those in pre-marketing studies; most AEFIs after vaccination were mild and common. More active surveillance studies should be performed to provide more comprehensive post-marketing safety data.

Predictors of poor seroconversion and adverse events to SARS-CoV-2 mRNA BNT162b2 vaccine in cancer patients on active treatment. Role of the Research Nurse.

Vaccines have shown 95% protection from COVID-19 disease in healthy populations. Initial findings in cancer patients suggest a lower seroconversion and greater toxicity possibly related to myelo-immunosuppressive therapies. We conducted a prospective study to assess factors predicting poor seroconversion and adverse events following immunization (AEFI) to the BNT162b2 vaccine in cancer patients on active treatment. Blood samples were collected by the research nurse at first dose (visit 1), second dose (visit 2), after 42 days (visit 3) and after 6 months (visit 4). At visit 1, 3 and 4 participants received: Hospital Anxiety and Depression Scale (HADS) and Distress Thermometer. Patients who ended treatment >6 months on active surveillance served as controls. Between March and July 2021, 320 subjects were recruited and 291 were assessable. The lack of seroconversion at 21 days from the second dose was 1.6% (95% CI, 0.4-8.7) on active surveillance, 13.9% (8.2-21.6) on chemotherapy, 11.4% (5.1-21.3) on hormone therapy, 21.7% (7.5-43.7) on targeted therapy and 4.8% (0.12-23.8) on immunotherapy. Compared to controls, the risk of no IgG response was greater for chemotherapy (P=0.033), targeted therapy (0.005) and hormonotherapy (P=0.051). Lymphocyte count less than 1x109/L, older age and advanced stage also significantly predicted poor seroconversion. Overall, 43 patients (14.8%) complained of AEFI, mostly of mild grade. Risk of AEFI was greater in females (P=0.001) and younger patients (P=0.009). A third booster dose and long-term serological testing is required in subjects who have not responded to the vaccine. nurses must take responsibility for promoting and protecting the health of cancer patients.

Evaluatıon of adverse events following immunization reported during national immunization programs (Between 2017-2019 in Ankara Province)

ABSTRACT Vaccination services are important in primary health-care service. The Expanded Programme on Immunization (EPI) began in 1981 in Turkey. Vaccines are generally safe products; although rare, undesirable effects may be observed after vaccination. In order to increase vaccination rates, vaccine acceptability and service quality; the Vaccine Adverse Event Reporting System (VAERS) and performing necessary interventions are indispensable parts of vaccination programs. This study aimed to evaluate Adverse Events Following Immunization (AEFI) cases during 2017–2019 in Ankara. A total of ~1.7 million doses of vaccine were administered, and only 71 adverse events following immunization (AEFI) were reported (0.41 cases/million doses of risk). AEFI forms were examined, and of these 71 cases, 17 (24%) were hospitalized and 54 (76%) were followed-up.

Evaluation of Vaccine Safety After the First Public Sector Introduction of Typhoid Conjugate Vaccine-Navi Mumbai, India, 2018.

BackgroundIn December 2017, the World Health Organization (WHO) prequalified the first typhoid conjugate vaccine (TCV; Typbar-TCV). While no safety concerns were identified in pre- and postlicensure studies, WHO’s Global Advisory Committee on Vaccine Safety recommended robust safety evaluation with large-scale TCV introductions. During July–August 2018, the Navi Mumbai Municipal Corporation (NMMC) launched the world’s first public sector TCV introduction. Per administrative reports, 113 420 children 9 months–14 years old received TCV.MethodsWe evaluated adverse events following immunization (AEFIs) using passive and active surveillance via (1) reports from the passive NMMC AEFI surveillance system, (2) telephone interviews with 5% of caregivers of vaccine recipients 48 hours and 7 days postvaccination, and (3) chart abstraction for adverse events of special interest (AESIs) among patients admitted to 5 hospitals using the Brighton Collaboration criteria followed by ascertainment of vaccination status.ResultsWe identified 222/113 420 (0.2%) vaccine recipients with AEFIs through the NMMC AEFI surveillance system: 211 (0.19%) experienced minor AEFIs, 2 (0.002%) severe, and 9 serious (0.008%). At 48 hours postvaccination, 1852/5605 (33%) caregivers reported ≥1 AEFI, including injection site pain (n = 1452, 26%), swelling (n = 419, 7.5%), and fever (n = 416, 7.4%). Of the 4728 interviews completed at 7 days postvaccination, the most reported AEFIs included fever (n = 200, 4%), pain (n = 52, 1%), and headache (n = 42, 1%). Among 525 hospitalized children diagnosed with an AESI, 60 were vaccinated; no AESIs were causally associated with TCV.ConclusionsNo unexpected safety signals were identified with TCV introduction. This provides further reassurance for the large-scale use of Typbar-TCV among children 9 months–14 years old.

Adverse events following immunization: orchestrated outcome of mothers' knowledge and behavior on vaccination practices

Background: Adverse events following immunization (AEFI) are a common occurrence in children after vaccination and can lead to loss of trust in the immunization program. Fear of AEFIs is a major factor implicated in ‘Vaccine Hesitancy’ as seen in countries with high vaccination coverage and low burden of vaccine preventable diseases. The study aimed at assessing the knowledge, attitudes and practices of mothers regarding AEFI and its impact on vaccination of their childrenMethods: A descriptive, cross sectional survey was conducted at the immunization clinic of a tertiary care hospital of western India. Mothers attending the immunization clinic were interviewed using a validated questionnaire. A sample size of 221 was derived based on the incidence of common AEFIs.Results: Awareness of AEFI was present in 86.4% participants while only 28% mothers confirmed that information regarding AEFIs was given to them at the time of immunization. Though awareness of minor side effects like fever (98%) and local reaction (85%) was good, less than 15% of the mothers were aware of serious AEFIs such as seizures and anaphylaxis. Only 66% mothers indicated that they would first consult their doctor in case of an adverse effect. Knowledge regarding true contraindications to vaccination was poor.Conclusions: Awareness of the possibility of AEFI was good and trust in immunization as a vital health intervention was intact. Awareness about serious AEFIs which necessitate prompt management was inadequate while that for minor side effects was satisfactory. Healthcare seeking behavior of mothers to serious AEFIs was appropriate.

Immunogenicity and safety of the inactivated poliomyelitis vaccine made from Sabin strains in a phase IV clinical trial for the vaccination of a large population

As a recently launched novel vaccine used as one of the vaccines for the final eradication of polios worldwide, complete data on the consistency and immunogenicity characteristics of the inactivated poliomyelitis vaccine made from the Sabin strain (sIPV) and its safety in large-scale populations are required to support the future use of this vaccine worldwide. A phase IV clinical trial was conducted to perform an immunogenicity evaluation of lot-to-lot consistency of three commercial batches of sIPV in 1200 infants and to investigate the vaccine’s safety on a large-scale in 20,019 infants for active monitoring and 29,683 infants for passive monitoring through the Adverse Event Following Immunization (AEFI) reporting system in China. In the immunogenicity evaluation, the average seroconversion rates for type I, type II and type III of the three groups were 99.83%, 98.93% and 99.44%, respectively. No differences in the seroconversion rate and the GMT ratios were noted in the pair-to-pair comparisons. In the large-scale safety evaluation, most adverse reactions occurred 0–30 days after the first doses, and the common local and systemic reactions were similar to those in the phase III clinical trial, with low incidence in both activated and passive monitoring. In conclusion, sIPV exhibits good lot-to-lot consistency and safety in large-scale populations; thus, it is qualified to serve as one of the vaccines for use in eradicating all wild and vaccine-derived polioviruses worldwide in the near future.Clinic Trial Registration. NCT04224519 and NCT04220515.

Epidemiological study of adverse events following immunization in under 5 year children

Background:The present study was conducted to study the socioeconomic and the demographic profile of children reporting with adverse events following immunization (AEFI) along with the determinants associated with AEFIs, based on investigation of each case and to assess the proportion of programmatic errors linked with AEFI cases.Materials and Methods:Record-based cross–sectional study conducted among sample of 118 cases of AEFI were reported. The case reports of all AEFI cases were procured and analyzed to identify factors associated with reported AEFI. The questionnaires related with preliminary investigation reports (PIRs) including forensic evidence of death cases were analyzed. Percentage analysis of data was done by proportions, measures of central tendencies, and Chi-square test.Results:Most of the cases reported were between 0 and 3 months of age constituting 39%. AEFI was seen more in male child than female. more than half of cases of AEFI were recorded following immunization with OPV/DPT/HBV together (66.94%). Most common AEFI reported were convulsion (68.64 %) and fever (58.47%) followed by local swelling at site of injection (11.86%). More than half of the cases of AEFI occurred within 12 hours of immunization (61.88%). Birth weight of most cases of AEFI were in the range between 2 and 2.4 kg (44.06%), followed by range between 2.5 and 2.9 kg (32.20%), the mean of birth weight was 2.51 kg.Conclusion:Convulsion was the most commonly reported AEFI, majority of AEFI occur within 12 h of immunization. Most of the AEFI were recorded following immunization with OPV/DPT/HBV together.

Adverse events following COVID-19 vaccination: first 90 days of experience from a tertiary care teaching hospital in South India.

Background:The COVID-19 vaccination program was introduced in India on 16 January 2021. The Government-issued fact sheet was the only source of information regarding Adverse Events Following Immunizations (AEFIs) for these vaccines. The objective of this study was to assess the AEFIs reported following COVID-19 vaccination in a tertiary care teaching hospital.Materials and methods:The spontaneous reporting method was used for data collection for a period of 3 months. A data collection form was designed to collect the data from the study population who reported adverse events. Collected data were analyzed and categorized by severity and seriousness. The causality assessment team performed causality assessment of the AEFIs using the World Health Organization’s causality assessment algorithm.Results:A total of 11,656 doses of COVID-19 vaccine were administered at the study site during the study period, of which 9292 doses were COVISHIELD™ and 2364 doses were COVAXIN™. In all, 445 AEFIs were reported from 269 subjects with an incidence rate of 3.48%. The majority of the subjects with AEFIs belonged to the age group of 18–45 years. Out of the total 445 AEFIs, 418 AEFIs were expected as per the fact sheets, 409 with COVISHIELD™ and 9 with COVAXIN™. Most of the AEFIs [62.02% (n = 276)] were observed at the system organ class of ‘General disorders and administration site conditions’. After the causality assessment, out of 433 AEFIs to COVISHIELDTM vaccine, 94.22% (n = 408) of events were categorized to have ‘consistent causal association with immunization’. Out of 12 adverse events following COVAXIN™, 8 (66.66%) events were categorized as ‘consistent causal association with immunization’. All of them recovered from their adverse events without any sequelae.Conclusion:Spontaneous reporting is one of the cheapest methods that can be used for the reporting of AEFI. This method helps health care professionals to identify rare events and potential signals.

Adverse Events Following Immunization Associated with Coronavirus Disease 2019 Vaccination Reported in the Mobile Vaccine Adverse Events Reporting System

BackgroundVaccination against coronavirus disease 2019 (COVID-19) is underway globally to prevent the infection caused by the severe acute respiratory syndrome coronavirus 2. We aimed to investigate the adverse events following immunization (AEFIs) for COVID-19 among healthcare workers (HCWs).MethodsThis was a retrospective study of the AEFIs associated with the first dose of the ChAdOx1 nCoV-19 vaccine at the Kosin University Gospel Hospital from March 3 to March 22, 2021. We investigated the systemic and local adverse events during the 7 days following the vaccination using the Mobile Vaccine Adverse Events Reporting System (MVAERS) developed by our hospital.ResultsA total of 1,503 HCWs were vaccinated, and the data of 994 HCWs were reported in the MVAERS. The most commonly reported AEFIs were tenderness at the injection site (94.5%), fatigue (92.9%), pain at the injection site (88.0%), and malaise (83.8%). The severity of most AEFIs was mild-to-moderate, and the severity and number of AEFIs were less in the older age group. There were no serious events requiring hospitalization, and most AEFIs improved within a few days.ConclusionThe AEFIs associated with the ChAdOx1 nCoV-19 vaccine were tolerable, and the use of the MVAERS was helpful in monitoring the AEFIs. The use of MVAERS will help in sharing accurate and ample information about vaccination against COVID-19.

Systemic and Neurologic Adverse Events Among 704,003 First-Dose Recipients of the Pfizer-Biontech (BNT162b2) mRNA COVID-19 Vaccine in Mexico

​Background: The development of mRNA vaccines to prevent SARS-CoV-2 has been remarkably successful, with highly effective vaccines available less than one year after confirming the first case. Due to the global burden of COVID-19 on health systems, emergency approval was attained after clinical trials with relatively small sample sizes and short follow-up periods. Limited information exists about the incidence of adverse events following immunisation (AEFI), particularly neurologic ones. Here, we describe the neurologic AEFI reported by recipients of the BNT162b2 mRNA COVID-19 vaccine. Methods: We conducted a prospective observational cohort using de-identified information from a database of all systemic and neurologic AEFI reported to the Mexican Ministry of Health throughout a passive Epidemiological Surveillance System by first-dose vaccine recipients, from December 24, 2020 to February 12, 2021. The cut-off date for this data was February 18, 2021. We performed descriptive analyses on demographics, timing from vaccination to AEFI development, event duration, and current outcome.Findings: Nationwide, 704 003 first-doses were administered; 6536 AEFI were reported. Among those, 4258 (65·1%) had at least one neurologic manifestation. Non-serious neurologic AEFI occurred in 99·6%. Headache (62·2%), transient sensory symptoms (3·5%), and weakness (1%) were the most frequent. Thirty-three serious AEFI were reported, of which 17 (2·4/100 000 doses) were neurologic, seven seizures, four functional syndromes, three Guillain-Barré syndrome (GBS) cases, and two of acute transverse myelitis. All GBS cases were related to a gastrointestinal infection before vaccination, 3/7 seizure episodes were related to poor antiepileptic drug compliance, and 2/7 to anaphylactic reactions. At the time of this report, 16/17 cases of serious neurologic AEFI had been discharged with no observed deaths.Interpretation: Our data suggest that the BNT162b2 mRNA vaccine is effective and safe. Their individual and societal benefits outweigh the low-percentage of serious neurologic and non-neurologic AEFI.Funding: Consejo Nacional de Ciencia y Tecnología, México.Declaration of Interest: None to declareEthical Approval: The study was revised and approved by the Ethics and Research Committees of the Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán (Ref. NER-3667-2021) and the Mexican Ministry of Health.

Coronavirus disease 2019 vaccines and relevant adverse reactions

In order to overcome the global pandemic of the new pathogen, severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), intensive research has been conducted to understand viral pathogenicity, establish effective treatment strategies, and develop vac cines against coronavirus disease 2019 (COVID-19). To prevent COVID-19, a variety of COVID-19 vaccines have been rapidly devel oped and are currently being administered worldwide. When developing new vaccines, monitoring for adverse events following immunization (AEFIs) has always been important, and some COVID-19 vaccines are particularly effective as new types of vaccines that have not been used before, thus attracting attention to AEFIs. Vaccine administration is carefully conducted while monitoring for AEFI that are being reported from time to time. AEFIs are largely divided into local reactions, systemic reactions, allergic reac tions, and adverse reactions to specific diseases or disease- attributable events. In addition, it is classified according to causes, but it is very difficult to confirm the association with the vaccine. Anaphylaxis, which is a systemic reaction among serious allergic reac tions, requires immediate treatment and may require testing to determine the cause. In order to increase the vaccination rate and secure herd immunity, there should be no fear of vaccination due to unidentified side effects. Therefore, monitoring of AEFIs is im portant and causal relationships must be well established based on reliable epidemiological investigations. Current data show that the benefits of a COVID-19 vaccine far outweigh the risk of AEFIs. Future studies should continue to understand the mechanisms and risk factors of identified adverse reactions. (Allergy Asthma Respir Dis 2021;9:124-135)