Effect of Delta variant on viral burden and vaccine effectiveness against new SARS-CoV-2 infections in the UK

Abstract

The effectiveness of the BNT162b2 and ChAdOx1 vaccines against new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections requires continuous re-evaluation, given the increasingly dominant B.1.617.2 (Delta) variant. In this study, we investigated the effectiveness of these vaccines in a large, community-based survey of randomly selected households across the United Kingdom. We found that the effectiveness of BNT162b2 and ChAdOx1 against infections (new polymerase chain reaction (PCR)-positive cases) with symptoms or high viral burden is reduced with the B.1.617.2 variant (absolute difference of 10–13% for BNT162b2 and 16% for ChAdOx1) compared to the B.1.1.7 (Alpha) variant. The effectiveness of two doses remains at least as great as protection afforded by prior natural infection. The dynamics of immunity after second doses differed significantly between BNT162b2 and ChAdOx1, with greater initial effectiveness against new PCR-positive cases but faster declines in protection against high viral burden and symptomatic infection with BNT162b2. There was no evidence that effectiveness varied by dosing interval, but protection was higher in vaccinated individuals after a prior infection and in younger adults. With B.1.617.2, infections occurring after two vaccinations had similar peak viral burden as those in unvaccinated individuals. SARS-CoV-2 vaccination still reduces new infections, but effectiveness and attenuation of peak viral burden are reduced with B.1.617.2.

Finger stick blood test to assess post vaccination SARS-CoV-2 neutralizing antibody response against variants

“…Meanwhile a more substantial reduction was seen in beta (47.8%, p <0.0001), gamma (49.5%, p <0.001) and delta variant preprint (which was not certified by peer review) is the author/funder, who has granted medRxiv a license to display the preprint in The copyright holder for this this version posted November 14, 2021. ; https://doi.org/10.1101/2021.11.11.21266241 doi: medRxiv preprint significant difference of nAb response was detected from WT for samples vaccinated within 3 months (Fig 4A). The modified cpVNT results agree with recent findings where BNT162b2 vaccine induced protection wanes within 4-5 months especially against the delta variant despite earlier findings suggest effective neutralization 19,20 . This demonstrates that this test can be effectively adapted in the event of future VOC emergence to quickly assess vaccinees' responses and even to identify vulnerable individuals for booster shots to prevent breakthrough infections.…”

Immune Evasive Effects of SARS-CoV-2 Variants to COVID-19 Emergency Used Vaccines

“…On the other hand, a study that vaccination was more effective in individuals aged 18 to 34 than in those aged 35 to 64 years, also in those showing signs of the prior SARS-CoV-2 infection than in those no infection. These results were confirmed by a study in populations vaccinated with ChAdOx1 or BNT162b2 SARS-CoV-2 vaccine (90,113). However, only 28.6% of immunosuppressed patients had detectable immune responses in humoral or T-cell responses after the first administration of ChAdOx1 nCoV-19 vaccine (114).…”

Waning Immunity after the BNT162b2 Vaccine in Israel

“…Second, Israel has followed the original Pfizer–BioNTech protocol of administering the second dose 3 weeks (21 days) after the initial injection in most recipients, whereas the time between doses in the United Kingdom has typically been longer. 6 …”