Coronavirus Disease 2019 Vaccination Coverage and Seropositivity amongst Nigerians 18 Years Old and Above.

BACKGROUND: This was a cross-sectional community-based survey to study the prevalence of serum antibodies against the severe acute respiratory syndrome coronavirus 1 (SARS-COV-1) and determine possible source of antibodies as to whether from vaccination or from natural infection as well as attempt to compare antibody levels in response to the different four types of vaccines administered in Nigeria. METHODS: A cross-sectional community-based study of the prevalence of serum antibodies against all four vaccine types used in Nigeria amongst a representative sample of people aged 18 years and above in the six geopolitical zones of the country using a multistage sampling technique covering 12 states of the country with two states being randomly selected from each geopolitical zone. High-throughput Roche electrochemiluminescence immunoassay system (Elecsys Anti-SARS-COV-1 Cobas) was used for qualitative and quantitative detection of antibodies to SARS-COV-1 in human plasma. RESULTS: There was no statistically significant difference between the proportions with seropositivity for both the vaccinated and the unvaccinated (P = 0.95). The nucleocapsid antibody (anti-Nc) titres were similar in both the vaccinated and the unvaccinated, whereas the Spike protein antibody (anti-S) titres were significantly higher amongst the vaccinated than amongst the unvaccinated. Antibody levels in subjects who received different vaccines were compared to provide information for policy. CONCLUSION: While only 45.9% of the subjects were reported to have been vaccinated, 98.7% of the subjects had had contact with the SARS-COV-1 as evidenced by the presence of nucleocapsid (NC) antibodies in their plasma. The 1.3% who had not been exposed to the virus, had spike protein antibodies which most likely resulted from vaccination in the absence of NC antibodies. Successive vaccination and booster doses either through heterogeneous or homologous vaccines increased antibody titres, and this stimulation of immune memory may offer greater protection against coronavirus disease 2019.

Cohort event monitoring for safety signal detection in adult individuals 18 years and above after immunisation with coronavirus disease 2019 vaccines in Nigeria.

Introduction: In Nigeria, immunisation with coronavirus disease 2019 (COVID-19) vaccines commenced in March 2021. COVISHIELD from AstraZeneca (AZ), a viral vector vaccine, was the brand administered in the first phase of vaccinations for pre-determined eligible adults 18 years and above. As more brands of COVID-19 vaccines have been introduced in Nigeria, identifying effective and safe vaccine brands is essential to pharmacovigilance and public health. The current study assessed the safety of the AZ-AZD1222 (ChAdOx1) COVID-19 vaccine in adults during the first phase of the vaccination exercise in Nigeria. Methodology: We conducted a descriptive analysis of safety data from selected vaccination sites across six states in Nigeria between June 2021 and September 2021. Respondents were monitored over 3 months for local and systemic reactions, as well as hospitalisation and mortality. Measures obtained from respondents include age, sex, pre-existing comorbidity, local and systemic reactions to vaccines, timing onset of reactions, hospitalisation and mortality. Bivariate and multivariable regression models were used to assess factors associated with vaccine reactogenicity. Results: A total of 1284 individuals were enrolled in the cohort study from the six selected states (Anambra, Borno, Edo, Katsina, Lagos and Plateau) representing the geopolitical zones of Nigeria. A total of 675 individuals or 52.6% of enrolees reported non-serious adverse effects, and only one individual or 0.08% reported a serious adverse event following immunisation in the first 7 days after vaccination. None of the enrolled participants reported adverse events requiring hospitalisation. The most common self-reported symptoms amongst vaccine recipients were tenderness at the injection site 20.9% and fever 20.3%. A majority of symptoms (55.5%) occurred on or before the 3rd day after vaccination. Multivariable logistic regression model showed that age 60 years or above (vs. 18-24 years) was significantly associated with a lower likelihood of a vaccine-related symptomatic reaction (adjusted odds ratio: 0.35; 95% confidence interval: 0.20-0.61). There was no reported mortality amongst all the enrolled and followed-up vaccine recipients. Conclusion: Our findings suggest that the safety profile of the AZ vaccine is acceptable, and the observed symptoms were mild and mostly within the first 3 days following vaccination. Vaccine recipients will benefit from counselling about potential transient reactions, and improving public awareness can potentially encourage the uptake of vaccines and reduce the spread of the COVID-19 pandemic.