Active surveillance of adverse events following immunization (AEFI): a prospective 3-year vaccine safety study

Surveillance for adverse events following immunization with DTaP-containing combination vaccines in Linping, China, 2019-2022

Background

The DTaP-Hib and DTaP-IPV/Hib combination vaccine can be used as a substitute for the diphtheria, tetanus, and acellular pertussis combined vaccine (DTaP). We aimed to evaluate the safety of multi-component vaccines containing DTaP by analyzing the reporting rates and characteristics of adverse events following immunization (AEFIs) in Linping District during the years 2019 to 2022.

Methods

We obtained data of AEFI and vaccination from the National AEFI Surveillance System of China and Zhejiang Municipal Immunization Information Management System, respectively, during 2019-2022 for a descriptive, epidemiological analysis.

Results

The total number of AEFI reported following vaccinations with DTaP-containing combination vaccines was 802 in Linping District from 2019 to 2022. The overall reporting rates of AEFIs following DTaP, DTaP-Hib, and DTaP-IPV/Hib vaccinations were 445.72 (537 cases), 536.29 (45 cases), and 306.13 (220 cases) per 100,000 doses in Linping District from 2019 to 2022, respectively. Only one case of a serious AEFI following DTaP vaccination, with a reporting rate of 0.83 per 100,000 doses. The composition ratio of vaccine product-related reactions for DTaP, DTaP-Hib, and DTaP-IPV/Hib were 99.81, 97.78, and 100.00%, respectively. The composition ratio of coincidental events for DTaP and DTaP-Hib were 0.19 and 2.22%, respectively. The reporting rates of total AEFIs for DTaP-IPV/Hib were lower than for DTaP. The reporting rate of local induration for DTaP-Hib was lower than for DTaP, and the reporting rates of local redness & swelling and local induration for DTaP-IPV/Hib were both lower than for DTaP. DTaP-IPV/Hib had a higher proportion of AEFIs in first quarter compared to DTaP. The reporting rate after the second dose of DTaP-Hib was higher than that of DTaP, and the reporting rates of AEFIs after the first dose and third dose of DTaP-IPV/Hib were lower than DTaP.

Conclusion

The reported AEFIs to multi-component vaccines containing DTaP components during 2019-2022 in Linping District were mainly mild vaccine reactions. DTaP-containing combination vaccines demonstrated a good safety profile.

Adverse Events Following Immunization Among Children Under Two Years of Age: A Prospective Observational Study From North India

BACKGROUND

Vaccination is one of the most cost-effective child survival health interventions. A single serious adverse event following immunization (AEFI) or a cluster of events may lead to a loss of public confidence in the program and a major setback to immunization coverage. This study was conducted to assess the incidence of AEFIs in children less than two years of age.

MATERIAL AND METHODS

A prospective community-based observational study was conducted in the North Indian state of Uttarakhand from October 2017 to February 2018. A total of 255 children who attended the selected sub-centres for immunization were finally included in the study. Follow-up home visits on the 8th and 30th day of vaccination were carried out to identify any occurrences of AEFIs.

RESULTS

Among 255 children, 212 AEFIs from 152 vaccinated subjects were reported. The majority of the AEFIs were reported in the age group 0-1 years. The incidence of AEFIs was 33.0 per 100 doses of vaccines administered. The most common AEFI reported was fever (101, 47.6%), followed by swelling (53, 25.0%). Among the vaccines, Pentavalent + oral polio vaccine (OPV) (48.8 per 100 doses) was majorly responsible for AEFIs, followed by diphtheria pertussis tetanus (DPT) + measles and rubella (MR) + OPV (46.6 per 100 doses).

CONCLUSION

Our findings revealed that although the incidence of AEFI reported was high, all of them were minor and no serious AEFIs were identified. The awareness among health professionals and the public regarding the reporting of AEFIs should be continued to increase the safety profile of vaccines.

Change in adverse event reporting following immunization of hepatitis B vaccine among infants between 2013 to 2020 before and after the vaccine administration law in China

Background

Hepatitis B vaccine (HepB) has been routinely recommended as part of the immunization program in China and has had a satisfactory safety and effectiveness profile in protecting infants from hepatitis B virus infection. We evaluated the surveillance sensitivity and changes over time of AEFI reports related to HepB among infants based on the consistent national data before and after the introduction of vaccine administration law (LAW) from 2013 to 2020 in China.

Methods

AEFI records were extracted from the Chinese National AEFI Surveillance System from 2013 to 2020. According to the proportion of different kinds of HepB vaccines distributed, the annual administration data of the most distributed HepB produced by Bio-Kangtai and its corresponding adverse reaction reports were collected and analyzed. We categorized the time interval into the pre-LAW period (2013 to 2017), transition period (2018 to 2019), and LAW period (2020) to demonstrate the impact of LAW on the surveillance patterns of AEFIs.

Results

The annual AEFI rates increased from 3.1/100,000 to 14.8/100,000 over this period in total. The rate ratio for the post-LAW period and pre-LAW period was 2.19 (95%CI: 2.10, 2.29). Common reactions occupied 87.6% of the total reported AEFIs whose rate was recorded as 7.9/100,000. Rare reactions occupied 9.1% of the total AEFIs showing an average rate of 0.8/100,000, of which anaphylaxis accounted for over 80%, with the rate ratio of the transition period and LAW period as 1.36 (95%CI:1.22, 1.52) and 1.14 (95%CI:0.95, 1.35), respectively. Children receiving more than one vaccine showed a higher proportion of fever, anaphylaxis, and febrile convulsions, which were suggested to be a result of vaccine co-administration vaccines, such as the DPT and Polio vaccine.

Conclusion

Most reactions were mild and self-limited and the rates of rare more serious events remained stable. The LAW has largely increased the surveillance capability and sensitivity on AEFIs of HepB and also contributes to enhancing public confidence in HepB immunization. Hepatitis B vaccination is a safe and effective means of preventing the complications of hepatitis B disease and continuous standardized AEFI investigation and assessment of causal association should be maintained.

Evaluation of the adverse events following immunization surveillance system, Ghana, 2019

BACKGROUND

With over 80% of children worldwide vaccinated, concerns about vaccine safety continues to be a public health issue. Ghana's Adverse Events Following Immunization surveillance started in 1978 with the objective to promptly detect and manage AEFI cases either real or perceived. Periodic evaluation of the surveillance system is critical for optimal performance; hence we evaluated the system to assess its attributes, usefulness and system's performance in meeting its objectives.

METHODS

A case of AEFI was defined as any untoward medical event occurring within 28 days after vaccination and may not necessarily have causal relationship with the vaccine use. We reviewed surveillance data and procedures for the period 2014 to 2018 and interviewed key stakeholders. Adapting the CDC's Updated Guidelines for Evaluating Public Health Surveillance Systems, we assessed the system's attributes and usefulness. We performed summary descriptive statistics on quantitative data and directed content analysis on information gathered from interviews.

RESULTS

In all, 2,282 AEFI cases including 476 (21%) serious cases (life threatening events) were reported for the period. The highest case detection rates of 61.45 AEFIs per 100,000 surviving infants was recorded in 2018. Reporting forms were modified to accommodate new indicators without any disruption in the function of the system. At the national level, completeness of 100 randomly sampled reporting forms (100%) and was higher than the region (27%) but timeliness (50%) was lower than the region (83%). All (16/16) Community Health Nurses interviewed indicated "fear of being victimized" as the reason for underreporting, nonetheless, the system was useful as it made them cautious when vaccinating children to prevent reactions. Data on AEFI surveillance was also useful in guiding training needs and provision of vaccination logistics.

CONCLUSION

The AEFI surveillance system is useful at all levels but partially meeting its objective due to underreporting. We recommend training and supportive supervision to improve timeliness of reporting, data completeness and acceptability.

Using Population-Based Structures to Actively Monitor AEFIs during a Mass Immunization Campaign-A Case of Measles-Rubella and Polio Vaccines

Active vaccine pharmacovigilance complements the standard passive or spontaneous surveillance system, which suffers from low reporting rates. This study aimed at utilizing population-based structures to report and profile adverse events following immunization (AEFI) with the measles and rubella vaccine (MR), or MR in combination with the bivalent oral polio vaccine (bOPV 1&3) (MR & bOPV), during mass vaccination in Uganda. Caretakers of children at home (less than 5 years) and schoolgoing children were followed up on and encouraged to report any AEFIs on day one, 2-3 days, 10 days, and 14 days after vaccination at school by their teachers and at-home, community-based village health teams. Out of 9798 children followed up on, 382 (3.9%) reported at least one AEFI, and in total, 517 AEFIs were reported. For MR, high temperature (21%), general feeling of weakness (19.3%), and headache (13%) were the most reported AEFIs, though there were variations on the days when they were reported. For the combination dose of MR & bOPV, high temperature (44%), rash (17%), general feeling of weakness (13%), and diarrhoea (8%) were the most common adverse events following immunization reported by caretakers. All 382 children cleared the AEFIs within 2 days, with 343 (90%) children reporting mild or moderate AEFIs and only 39 (10%) reporting severe AEFIs. The reported AEFIs are known and are mentioned in the vaccine leaflets with similar severity classification. Rates of AEFIs differed with the number of days after receiving the immunization. Conclusion: Active surveillance for AEFIs provides additional important information to national vaccine regulatory bodies. It reassures the public that vaccines are safe and that their safety is being taken seriously in Uganda, which would improve vaccine acceptability and confidence in the health system. Piggybacking on existing structures such as village health team members (for children at home) and teachers (for schoolgoing children) facilitates reaching vaccine recipients and increases reporting rates. Therefore, studies using active reporting of AEFIs should be conducted at regular intervals to report the overall incidence of AEs and to monitor trends and changes.

How were DTP-related adverse events reduced after the introduction of an acellular pertussis vaccine in Chile?

Chile has a passive surveillance system of adverse events following immunization (AEFI) that allows monitoring and evaluating the safety profile of the vaccines administered. Between 2018 and 2019, the National Immunization Program (NIP) changed from a pentavalent whole-cell pertussis vaccine (wP) to a hexavalent (DTaP-IPV-HepB-Hib) acellular pertussis vaccine (aP) for children <2 years.

Causality assessment of adverse events following immunization: the problem of multifactorial pathology

The analysis of Adverse Events Following Immunization (AEFI) is important in a balanced epidemiological evaluation of vaccines and in the issues related to national vaccine injury compensation programs. If manufacturing defects or vaccine storage and delivering errors are excluded, the majority of adverse reactions to vaccines occur as excessive or biased inflammatory and immune responses. These unwanted phenomena, occasionally severe, are associated with many different endogenous and exogenous factors, which often interact in complex ways. The confirmation or denial of the causal link between an AEFI and vaccination is determined pursuant to WHO guidelines, which propose a four-step analysis and algorithmic diagramming. The evaluation process from the onset considers all possible "other causes" that can explain the AEFI and thus exclude the role of the vaccine. Subsequently, even if there was biological plausibility and temporal compatibility for a causal association between the vaccine and the AEFI, the guidelines ask to look for any possible evidence that the vaccine could not have caused that event. Such an algorithmic method presents some concerns that are discussed here, in the light of the multifactorial nature of the inflammatory and immune pathologies induced by vaccines, including emerging knowledge of genetic susceptibility to adverse effects. It is proposed that the causality assessment could exclude a consistent association of the adverse event with the vaccine only when the presumed "other cause" is independent of an interaction with the vaccine. Furthermore, the scientific literature should be viewed not as an exclusion criterion but as a comprehensive analysis of all the evidence for or against the role of the vaccine in causing an adverse reaction. These issues are discussed in relation to the laws that, in some countries, regulate the mandatory vaccinations and the compensation for those who have suffered serious adverse effects.

Causality assessment of adverse events following immunization: the problem of multifactorial pathology

The analysis of Adverse Events Following Immunization (AEFI) is important in a balanced epidemiological evaluation of vaccines and in the issues related to vaccine injury compensation programs. The majority of adverse reactions to vaccines occur as excessive or biased inflammatory and immune responses. These unwanted phenomena, occasionally severe, are associated with many different endogenous and exogenous factors, which often interact in complex ways. The confirmation or denial of the causal link between an AEFI and vaccination is determined pursuant to WHO guidelines, which propose a four-step analysis and algorithmic diagramming. The evaluation process from the onset considers all possible "other causes" that might explain the AEFI and thus exclude the role of the vaccine. Subsequently, even if there was biological plausibility and temporal compatibility for a causal association between the vaccine and the AEFI, the guidelines ask to look for any possible evidence that the vaccine could not have caused that event. Such an algorithmic method presents several concerns that are discussed here, in the light of the multifactorial nature of the inflammatory and immune pathologies induced by vaccines, including emerging knowledge of genetic susceptibility to adverse effects. It is proposed that the causality assessment could exclude a consistent association of the adverse event with the vaccine only when the presumed "other cause" is independent of an interaction with the vaccine. Furthermore, the scientific literature should be viewed not as an exclusion criterion but as a comprehensive analysis of all the evidence for or against the role of the vaccine in causing an adverse reaction. Given these inadequacies in the evaluation of multifactorial diseases, the WHO guidelines need to be reevaluated and revised. These issues are discussed in relation to the laws that, in some countries, regulate the mandatory vaccinations and the compensation for those who have suffered serious adverse effects.