Common Adverse Events from Mixing COVID-19 Vaccine Booster in Hanoi, Vietnam

Adverse Events Following Immunization with Novel Oral Polio Vaccine Type 2, and the Experience and Challenges of Reporting in Sierra Leone

Background

The manifestation and spread of neuroinvasive circulating vaccine-derived polioviruses (cVDPVs) across several countries, which led to the emergency use of the novel oral polio vaccine type 2 (nOPV2), raised concerns about adverse events following immunization (AEFI) surveillance. We assessed the attributes of AEFI with nOPV2 and examined stakeholder experiences and challenges in AEFI surveillance in Sierra Leone.

Methods

Using a mixed method approach, we retrospectively reviewed passive data collected during a 2021 immunization campaign, and conducted semi-structured, interviews with vaccinators, district AEFI focal persons, and key stakeholders at the national Expanded Program on Immunization and the National Medicines Regulatory Authority. AEFI were categorized using the Medical Dictionary for Regulatory Activities (MedDRA) Preferred Terms (PTs) and System Organ Class (SOC). Outcomes were stratified as recovered or not, with preventability and causality assessed using the Schumock and Thornton and World Health Organization (WHO) algorithms, respectively.

Results

A total of 528 suspected AEFI were documented, predominantly affecting children aged 28 days to 23 months (63.3%). Most reported AEFI were administration site conditions and general disorders, with pyrexia being the predominant PT. Of 80 serious cases, 78 recovered, with 74 having an inconsistent causal relationship with the vaccine. Most serious cases (78) were deemed non-preventable, with only two being probably preventable. AEFI reporting was not routinely carried out across the group of people interviewed. AEFI reporting was not consistently performed, with discrepancies in defining reportable events and confusion over responsibility. Challenges with the open data kit (ODK) platform were noted, along with perceived inadequacies in training.

Conclusion

While the nOPV2 is relatively new, the majority of AEFI were not serious, and most serious cases were not causally linked to the vaccine. Participants exhibited variations in experience and awareness of AEFI reporting.

Sex Differences in Serious Adverse Events Reported Following Booster Doses of COVID-19 Vaccination in Thailand: A Countrywide Nested Unmatched Case-Control Study

A booster dose of a COVID-19 vaccine has been proven effective in restoring vaccine effectiveness and is currently recommended for use in some populations at risk of severe COVID-19 infection. Since sex differences in adverse events are significant in response to the vaccines, the safety of booster selection must be studied to avoid serious adverse events (SAE), such as life-threatening diseases. First, this study aimed to identify sex differences in SAE incidences using a prospective cohort design. Second, a nested unmatched case-control study was used to identify factors associated with reported SAE within 30 days after the booster shot. Multivariable logistic regression indicated the adjusted odds ratio by accounting for host and vaccine variables, thus, policy effects. The findings confirmed that SAE was rare and that age-sex-dominated disease classifications differed. Specific to SAE following the booster dose, we found that females aged 12-40 had a higher risk of being reported with SAE than males of the same age, while males over 50 had a higher risk than females. Other risk factors identified were the presence of metabolic syndrome and the use of certain vaccine brands. Mechanisms could be explained by individual host responses rather than the vaccines' direct effect. Therefore, SAE could be preventable by age-sex-specific vaccine selection, post-vaccination precautions, and early symptom detection. Future vaccine development should aim to limit host-specific reactogenicity for safety concerns.