Sustained spike-specific IgG antibodies following CoronaVac (Sinovac) vaccination in sub-Saharan Africa, but increased breakthrough infections in baseline spike-naive individuals

Abstract

IntroductionThis study investigated the antibody responses to the inactivated COVID-19 vaccine, CoronaVac (Sinovac Biotech) in the African population to provide valuable insights into long-term immunity and breakthrough infections against SARS-CoV-2 in individuals with varying prior IgG seropositivity.MethodsReal-life cohorts were used to longitudinally track antibody levels against the SARS-CoV-2 spike and nucleoprotein in 60 participants over 12 months to examine the levels of multiple antibody isotypes (S-IgG, S-IgM, S-IgA, N-IgG, and N-IgM).ResultsThroughout the 12 months, we observed consistently high and stable seropositivity rates for spike-IgG antibodies, spike-IgM antibodies showed a decline in frequencies over time, and spike-IgA levels remained moderate and stable. Vaccinated individuals previously positive for spike-IgG antibodies demonstrated strong and persistent seropositivity, while those initially negative experienced a gradual and delayed increase in seropositivity rates. The fold change analysis of S- and N- antibody responses demonstrated a consistently stable and comparable profile over time, indicating that vaccine-induced antibody responses remain constant and lack significant fluctuations beyond the initial boost. The study emphasized that individuals lacking previous IgG positivity showed reduced vaccine-induced spike-IgG antibodies and were more susceptible to breakthrough infections, highlighting their higher vulnerability. All cases of breakthrough infections were asymptomatic, indicating the conferred protection to the vaccinated individuals.DiscussionThe findings corroborated earlier studies on the effectiveness of the CoronaVac vaccine and emphasized the significance of accounting for pre-existing seropositivity in vaccine assessments. This study effectively demonstrated durable antibody responses against SARS-CoV-2 in the African population following the CoronaVac vaccination, providing crucial insights for informing vaccination strategies and safeguarding vulnerable populations. Continuous surveillance is imperative for tracking breakthrough infections and monitoring waning immunity. The insights gained offer crucial direction for public health strategies and enhance comprehension of vaccine effectiveness in sub-Saharan Africa. Further research should explore functional outcomes, cellular immune responses, and the vaccine’s effectiveness against different variants to enhance our understanding and optimize vaccine strategies.

The subdued post-boost spike-directed secondary IgG antibody response in Ugandan recipients of the Pfizer-BioNTech BNT162b2 vaccine has implications for local vaccination policies

“…The rapid spike-directed IgG response within two weeks of the initial vaccine dose concurred with global trends and highlighted the vaccine’s effectiveness across varied demographics ( 22 ). We noted consistent levels of S-IgG antibodies after boosting, aligning with some populations ( 23 ), and with other vaccine types administered in this population ( 24 , 25 ), but contrasts with others where levels distinctly declined 4-6 months post-vaccination ( 26 – 28 ). The antibody persistence in our Ugandan cohort suggests a potential benefit in modifying the boosting interval, as supported by mouse models ( 29 ), and the need to optimise vaccination strategies in this population.…”

The single-dose Janssen Ad26.COV2.S COVID-19 vaccine elicited robust and persistent anti-spike IgG antibody responses in a 12-month Ugandan cohort

“…Furthermore, breakthrough infections were more frequent among the participants who were S-IgG seronegative at baseline, thus suggesting an advantage of multiple antigenic exposure in eliciting protective vaccine-induced antibodies. Our findings also align with responses elicited by other COVID-19 vaccines used in this demographic, such as Sinovac Biotech’s CoronaVac COVID-19 vaccine ( 30 ), the Oxford/AstraZeneca ChadOx1-S COVID-19 vaccine ( 31 ), the Pfizer-BioNTech BNT162b2 Vaccine ( 24 ), and Moderna’s mRNA 1273 ( 25 ) collectively supporting the vaccine’s effectiveness in this landscape and could have implications for future vaccination and public health strategies ( 32 – 34 ).…”