Immunological insights into COVID-19 in Southern Nigeria.

Introduction: One of the unexpected outcomes of the COVID-19 pandemic was the relatively low levels of morbidity and mortality in Africa compared to the rest of the world. Nigeria, Africa's most populous nation, accounted for less than 0.01% of the global COVID-19 fatalities. The factors responsible for Nigeria's relatively low loss of life due to COVID-19 are unknown. Also, the correlates of protective immunity to SARS-CoV-2 and the impact of pre-existing immunity on the outcome of the COVID-19 pandemic in Africa are yet to be elucidated. Here, we evaluated the natural and vaccine-induced immune responses from vaccinated, non-vaccinated and convalescent individuals in Southern Nigeria throughout the three waves of the COVID-19 pandemic in Nigeria. We also examined the pre-existing immune responses to SARS-CoV-2 from samples collected prior to the COVID-19 pandemic. Methods: We used spike RBD and N- IgG antibody ELISA to measure binding antibody responses, SARS-CoV-2 pseudotype assay protocol expressing the spike protein of different variants (D614G, Delta, Beta, Omicron BA1) to measure neutralizing antibody responses and nucleoprotein (N) and spike (S1, S2) direct ex vivo interferon gamma (IFNγ) T cell ELISpot to measure T cell responses. Result: Our study demonstrated a similar magnitude of both binding (N-IgG (74% and 62%), S-RBD IgG (70% and 53%) and neutralizing (D614G (49% and 29%), Delta (56% and 47%), Beta (48% and 24%), Omicron BA1 (41% and 21%)) antibody responses from symptomatic and asymptomatic survivors in Nigeria. A similar magnitude was also seen among vaccinated participants. Interestingly, we revealed the presence of preexisting binding antibodies (N-IgG (60%) and S-RBD IgG (44%)) but no neutralizing antibodies from samples collected prior to the pandemic. Discussion: These findings revealed that both vaccinated, non-vaccinated and convalescent individuals in Southern Nigeria make similar magnitude of both binding and cross-reactive neutralizing antibody responses. It supported the presence of preexisting binding antibody responses among some Nigerians prior to the COVID-19 pandemic. Lastly, hybrid immunity and heterologous vaccine boosting induced the strongest binding and broadly neutralizing antibody responses compared to vaccine or infection-acquired immunity alone.

COVID-19 vaccine hesitancy in six geopolitical zones in Nigeria: a cross-sectional survey.

Introduction: the high expectations that heralded the development of COVID-19 vaccines has been plagued with vaccine hesitancy (VH). The prevalence and associated factors of COVID-19 VH in the six geopolitical zones in Nigeria are explored. Methods: using a cross sectional survey, a pre-tested and validated questionnaire on a "Google form" was distributed via social media platforms and hard copies in the six geopolitical zones of Nigeria. Included, using a chain-reference sampling technique, were healthcare workers (HCW), university students and adults in the general population. Participants who expressed unwillingness to receive COVID-19 vaccine in the event of an available vaccine were considered to have vaccine hesitancy. Frequency and percentage were used to describe categorical variables. Multivariable logistic regression analysis was used to assess for factors associated with VH. Level of significance was set at 5% on two-sided tails test. Results: among 1615 respondents, mean (standard deviation) age was 36.7 (11.3) years, and 847 (52.4%) were males. More than half were healthcare workers (943; 58.4%), 97.4% had at least secondary level of education, and majority 60.5% belonged to the upper social class. The prevalence of VH was 68.5% (1107/1615), and 67.2% preferred foreign manufactured COVID-19 vaccines. On multivariable regression analysis, residence in Northeast (AOR 6.01, 95% CI 2.24, 16.10) and Northwest (AOR 3.33, 95% CI 1, 48, 7.48) geopolitical zones, the Igbo ethnic group (AOR 1.88, 95% 1.10, 3.22), Christians (AOR 1.86, 95% 1.10, 3.14), nurses (AOR 3.50, 95% CI 1.25, 9.80), pharmacist (AOR 5.82, 95% CI 2.12, 16.32) and participants without confidence in foreign vaccines (AOR 4.13, 95% CI 2.99, 5.72) were at higher likelihood of VH. Conclusion: vaccine hesitancy is high among adults in Nigeria, with higher likelihood among the Igbo ethnic group, Christian faith, residence in Northeast and Northwest geopolitical zones and those with an aversion to foreign-made vaccines. Targeted interventions are required for the desired COVID-19 vaccine uptake rate and herd immunity.