RESUMO
Currently approved COVID-19 vaccines prevent symptomatic infection, hospitalization, and death of the disease. However, the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants raises concerns of reduced vaccine effectiveness and increased risk of infection. Repeated homologous booster in elderly individuals and immunocompromised patients is considered to solve severe form of disease caused by new SARS-CoV-2 variants but cannot protect completely against breakthrough infection. In our previous study we assessed the immunogenicity of an adenovirus-based vaccine expressing SARS-CoV-2-S1 (Ad5.S1) in mice, resulting in that a single immunization with Ad5.S1, via subcutaneously injection or intranasal delivery, induced robust humoral and cellular immune responses [1]. As a follow up study, here we showed that vaccinated mice had high titers of anti-S1 antibodies at one year after vaccination compared to PBS immunized mice. Furthermore, one booster dose of non-adjuvanted recombinant S1Beta (rS1Beta) subunit vaccine was effective in stimulating strong long-lived S1-specific immune responses and inducing significantly high neutralizing antibodies against the Wuhan, Beta, and Delta strain with 3.6- to 19.5-fold change increases. Importantly, the booster dose elicits cross-reactive antibody responses resulting in ACE2 binding inhibition against spike of SARS-CoV-2 variants (Wuhan, Alpha, Beta, Gamma, Delta, Zeta, Kappa, New York, India) as early as two-week post-boost injection, persisting over 28 weeks after a booster vaccination. Interestingly, levels of neutralizing antibodies were correlated with not only level of S1-binding IgG but also level of ACE2 inhibition in the before- and after-booster serum samples. Our findings show that S1 recombinant protein subunit vaccine candidate as a booster has potential to offer cross-neutralization against broad variants, and has important implications for vaccine control of new emerging breakthrough SARS-CoV-2 variants in elderly individuals primed with adenovirus-based vaccine like AZD1222 and Ad26.COV2.S.
RESUMO
Background and objectiveSARS-CoV-2 infection poses tremendous challenge to the healthcare system of nations across the globe. Serological testing for SARS-CoV-2 infection in healthcare workers, which form a high-risk group, helps in identifying the burden of hidden infection in an institutional setting. MethodsWe present the results of a cross-sectional serosurvey in healthcare workers from two different hospital settings based on their role in the management of SARS-CoV-2 patients in District Srinagar, Kashmir. In addition to testing for the presence of SARS-CoV-2 specific IgG, we collected information on influenza-like symptoms in the last four weeks and the status of RT-PCR testing. SARS-CoV-2 specific IgG antibodies were detected in serum samples using a sensitive and specific chemiluminescent microparticle immunoassay technology. Interpretation and ConclusionOf 2915 healthcare workers who participated in the study, we analysed data from 2905 healthcare workers. The overall prevalence of SARS-CoV-2 specific IgG antibodies was 2.5% (95% CI 2.0-3.1) in the healthcare workers of District Srinagar. Healthcare workers who had ever worked at a dedicated-COVID hospital had a substantially lower seroprevalence of 0.6% (95% CI: 0.2 - 1.9). Among healthcare workers who had tested positive for RT-PCR, seroprevalence was 27.6% (95% CI: 14.0 - 47.2).The seroprevalence of SARS-CoV-2 infection in healthcare workers of District Srinagar is low, reflecting that a high proportion of healthcare workers are still susceptible to the infection. It is crucial to lay thrust on infection prevention and control activities and standard hygiene practices by the healthcare staff to protect them from acquiring infection within the healthcare setting.