Use of whole genome sequencing to estimate the contribution of immune evasion and waning immunity to decreasing COVID-19 vaccine effectiveness during alpha and delta variant waves

BackgroundThe decline in COVID-19 mRNA vaccine effectiveness (VE) is well established, however the impact of variant-specific immune evasion and waning protection remains unclear. Here, we use whole-genome-sequencing (WGS) to tease apart the contribution of these factors on the decline observed following the introduction of the Delta variant. Further, we evaluate the utility of calendar-period-based variant classification as an alternative to WGS. MethodsWe conducted a test-negative-case-control study among people who received SARS-CoV-2 RT-PCR testing in the Yale New Haven Health System between April 1 and August 24, 2021. Variant classification was performed using WGS and secondarily by calendar-period. We estimated VE as one minus the ratio comparing the odds of infection among vaccinated and unvaccinated people. ResultsOverall, 2,029 cases (RT-PCR positive, sequenced samples) and 343,985 controls (negative RT-PCRs) were included. VE 14-89 days after 2nd dose was significantly higher against WGS-classified Alpha infection (84.4%, 95% confidence interval: 75.6-90.0%) than Delta infection (68.9%, CI: 58.0-77.1%, p-value: 0.013). The odds of WGS-classified Delta infection were significantly higher 90-149 than 14-89 days after 2nd dose (Odds ratio: 1.6, CI: 1.2-2.3). While estimates of VE against calendar-period-classified infections approximated estimates against WGS-classified infections, calendar-period-based classification was subject to outcome misclassification (35% during Alpha period, 4% during Delta period). ConclusionsThese findings suggest that both waning protection and variant-specific immune evasion contributed to the lower effectiveness. While estimates of VE against calendar-period-classified infections mirrored that against WGS-classified infections, our analysis highlights the need for WGS when variants are co-circulating and misclassification is likely. Summary of main pointsUsing whole genome sequencing, we provide direct evidence of waning vaccine effectiveness and variant-specific immune evasion during the Delta wave. Effectiveness estimates against calendar-period-classified infections approximated estimates against WGS-classified infections, however, calendar-period classification was associated with a variant misclassification.

In vitro and in vivo preclinical studies predict REGEN-COV protection against emergence of viral escape in humans

Monoclonal antibodies against SARS-CoV-2 are a clinically validated therapeutic option against COVID-19. As rapidly emerging virus mutants are becoming the next major concern in the fight against the global pandemic, it is imperative that these therapeutic treatments provide coverage against circulating variants and do not contribute to development of treatment emergent resistance. To this end, we investigated the sequence diversity of the spike protein and monitored emergence of minor virus variants in SARS-COV-2 isolates found in COVID-19 patients or identified from preclinical in vitro and in vivo studies. This study demonstrates that a combination of non-competing antibodies, REGEN-COV, not only provides full coverage against current variants of concern/interest but also protects against emergence of new such variants and their potential seeding into the population in a clinical setting.