ABSTRACT
BackgroundBooster vaccine doses offer protection against severe COVID-19 caused by omicron but are less effective against infection. Characteristics such as serological correlates of protection, viral abundance, and clearance of omicron infection in triple vaccinated individuals are scarce. MethodsWe conducted a 4-week twice-weekly SARS-CoV-2 qPCR screening shortly after an mRNA vaccine booster in 368 healthcare workers. Spike-specific IgG levels and neutralization titers were determined at study start. qPCR-positive participants were sampled repeatedly for two weeks and monitored for symptoms. ResultIn total 81 (cumulative incidence 22%) omicron infections were detected, divided between BA.1, BA.1.1 and BA.2. Increasing post-booster antibody titers were protective against infection (p<0.05), linked to reduced viral load (p<0.01) and time to viral clearance (p<0.05). Only 10% of infected participants remained asymptomatic through the course of their infection. Viral load peaked at day 3 and live virus could be detected for up to 9 days after first PCR-positive sample. Presence of symptoms correlated to elevated viral load (p<0.0001), but despite resolution of symptoms most participants showed Ct levels <30 at day 9. No significant differences were observed for viral load and time to viral clearance between BA.1, BA.1.1 and BA.2 infected individuals. ConclusionWe report a high incidence of omicron infection despite recent booster vaccination in triple vaccinated individuals. Increasing levels of vaccine-induced spike-specific WT antibodies entail increased protection against infection and reduce viral load if infected. High viral load and secretion of live virus for up to nine days may facilitate transmission in a triple vaccinated population.
ABSTRACT
People with previous SARS-CoV-2 infection mount potent immune responses to COVID-19 vaccination, but long-term effects of prior infection on these immune responses are unknown. We investigated the long-term impact of prior SARS-CoV-2 infection on humoral and cellular immune responses in healthcare workers receiving the mRNA BNT162b2 or the adenovirus vectored ChAdOx1 nCoV-19 vaccine. Vaccination with both vaccine platforms resulted in substantially enhanced T cell immune responses, antibody responses to spike and neutralizing antibodies effective against ten SARS-CoV-2 variants following SARS-CoV-2 infection, compared to in naive individuals. The enhanced immune responses sustained over seven months following vaccination. These findings imply that prior infection should be taken into consideration when planning booster doses and design of current and future COVID-19 vaccine programs. One-Sentence SummarySARS-CoV-2 infection prior to vaccination leads to substantial and durable increases in immune memory responses.
ABSTRACT
BackgroundSARS-CoV-2 variants, such as Alpha, Beta, Gamma and Delta, are raising concern about the efficiency of neutralizing antibodies (NAb) induced by wild-type infection or vaccines based on the wild-type spike. MethodsWe determined IgG and NAb against SARS-CoV-2 variants one year following mild wild-type infection (n=104) and two-dose regimens with BNT162b2 (BNT/BNT) (n=67), ChAdOx1 (ChAd/ChAd) (n=82), or heterologous ChAdOx1 followed by BNT162b2 (ChAd/BNT) (n=116). FindingsWild type spike IgG and NAb remained detectable in 80% (83/104) of unvaccinated participants one year post mild infection. The neutralizing capacity was similar against wild type (reference), Alpha (0.95 (0.92-0.98) and Delta 1.03 (0.95-1.11) but significantly reduced against Beta (0.54 (0.48-0.60)) and Gamma 0.51 (0.44-0.61). Similarly, BNT/BNT and ChAd/ChAd elicited sustained capacity against Alpha and Delta (1.01 (0.78-1.31) and 0.85 (0.64-1.14)) and (0.96 (0.84-1.09) and 0.82 (0.61-1.10) respectively), with reduced capacity against Beta (0.67 (0.50-0.88) and 0.53 (0.40-0.71)) and Gamma (0.12 (0.06-0.27) and 0.54 (0.37-0.80)). A similar trend was found following ChAd/BNT (0.74 (0.66-0.83) and 0.70 (0.50-0.97) against Alpha and Delta and 0.29 (0.20-0.42) and 0.13 (0.08-0.20) against Beta and Gamma). InterpretationPersistent neutralization of the wide-spread Alpha and Delta variants one year after wild-type infection may aid vaccine policy makers in low-resource settings when prioritizing vaccine supply. The reduced capacity of neutralizing Beta and Gamma strains, but not the Alpha and Delta strains following both infection and three different vaccine regimens argues for caution against Beta and Gamma-exclusive mutations in the efforts to optimize next generation SARS-CoV-2 vaccines. FundingA full list of funding bodies that contributed to this study can be found in the Acknowledgements section
ABSTRACT
BackgroundRecent reports demonstrate robust serological responses to a single dose of messenger RNA (mRNA) vaccines in individuals previously infected with SARS-CoV-2. Data on immune responses following a single-dose adenovirus-vectored vaccine expressing the SARS-CoV-2 spike protein (ChAdOx1 nCoV-19) in individuals with previous SARS-CoV-2 infection are however limited, and current guidelines recommend a two-dose regime regardless of preexisting immunity. MethodsWe compared spike-specific IgG and pseudo-neutralizing spike-ACE2 blocking antibodies against SARS-CoV-2 wild type and variants B.1.1.7, B.1.351, and P1 following two doses of the mRNA vaccine BNT162b2 and a single dose of the adenovector vaccine ChAdOx1 nCoV-19 in 232 healthcare workers with and without previous COVID-19. FindingsThe post-vaccine levels of spike-specific IgG and neutralizing antibodies against the SARS-CoV-2 wild type and all three variants of concern were similar or higher in participants receiving a single dose of ChAdOx1 nCoV-19 vaccine post SARS-CoV-2 infection (both < 11 months post infection (n=37) and [≥] 11 months infection (n=46)) compared to participants who received two doses of BNT162b2 vaccine (n=149). InterpretationOur data support that a single dose ChAdOx1 nCoV-19 vaccine serves as an effective immune booster after priming with natural SARS-CoV-2 infection up to at least 11 months post infection.
