Effectiveness of the Pfizer-BioNTech and Oxford-AstraZeneca vaccines on covid-19 related symptoms, hospital admissions, and mortality in older adults in England: test negative case-control study

Abstract

Objective To estimate the real world effectiveness of the Pfizer-BioNTech BNT162b2 and Oxford-AstraZeneca ChAdOx1-S vaccines against confirmed covid-19 symptoms (including the UK variant of concern B.1.1.7), admissions to hospital, and deaths. Design Test negative case-control study. Setting Community testing for covid-19 in England. Participants 156 930 adults aged 70 years and older who reported symptoms of covid-19 between 8 December 2020 and 19 February 2021 and were successfully linked to vaccination data in the National Immunisation Management System. Interventions Vaccination with BNT162b2 or ChAdOx1-S. Main outcome measures Primary outcomes were polymerase chain reaction confirmed symptomatic SARS-CoV-2 infections, admissions to hospital for covid-19, and deaths with covid-19. Results Participants aged 80 years and older vaccinated with BNT162b2 before 4 January 2021 had a higher odds of testing positive for covid-19 in the first nine days after vaccination (odds ratio up to 1.48, 95% confidence interval 1.23 to 1.77), indicating that those initially targeted had a higher underlying risk of infection. Vaccine effectiveness was therefore compared with the baseline post-vaccination period. Vaccine effects were noted 10 to 13 days after vaccination, reaching a vaccine effectiveness of 70% (95% confidence interval 59% to 78%), then plateauing. From 14 days after the second dose a vaccination effectiveness of 89% (85% to 93%) was found compared with the increased baseline risk. Participants aged 70 years and older vaccinated from 4 January (when ChAdOx1-S delivery commenced) had a similar underlying risk of covid-19 to unvaccinated individuals. With BNT162b2, vaccine effectiveness reached 61% (51% to 69%) from 28 to 34 days after vaccination, then plateaued. With ChAdOx1-S, effects were seen from 14 to 20 days after vaccination, reaching an effectiveness of 60% (41% to 73%) from 28 to 34 days, increasing to 73% (27% to 90%) from day 35 onwards. On top of the protection against symptomatic disease, a further 43% (33% to 52%) reduced risk of emergency hospital admission and 51% (37% to 62%) reduced risk of death was observed in those who had received one dose of BNT162b2. Participants who had received one dose of ChAdOx1-S had a further 37% (3% to 59%) reduced risk of emergency hospital admission. Follow-up was insufficient to assess the effect of ChAdOx1-S on mortality. Combined with the effect against symptomatic disease, a single dose of either vaccine was about 80% effective at preventing admission to hospital with covid-19 and a single dose of BNT162b2 was 85% effective at preventing death with covid-19. Conclusion Vaccination with either one dose of BNT162b2 or ChAdOx1-S was associated with a significant reduction in symptomatic covid-19 in older adults, and with further protection against severe disease. Both vaccines showed similar effects. Protection was maintained for the duration of follow-up (>6 weeks). A second dose of BNT162b2 was associated with further protection against symptomatic disease. A clear effect of the vaccines against the B.1.1.7 variant was found.

Reduced sensitivity of infectious SARS-CoV-2 variant B.1.617.2 to monoclonal antibodies and sera from convalescent and vaccinated individuals

“…These results are in line with the real-world efficacy of the two vaccines. The Pfizer vaccine is known to be protective against asymptomatic and symptomatic infections, including severe diseases, induced by B.1.1.7 and B.1.351, as described for instance in the UK, Israel and South Africa [46][47][48] In contrast, the efficacy of a two-dose regimen of AstraZeneca against mild-to-moderate disease dropped to 10% in South Africa, where the B.1.351 variant circulates 49 . Altogether, our results suggest that a single dose of AstraZeneca vaccine will not display an optimal protection against B.1.617.2.…”

Reported adverse effects following COVID-19 vaccination at a tertiary care hospital, focus on cerebral venous sinus thrombosis (CVST)

“…Evidence on the safety of COVID-19 vaccines continue to emerge, a larger prospective observational studies in a country like United Kingdome with mass vaccination campaigns showed lower frequencies of adverse effects than reported in phase III trials [ 15 ]. Real world data in elderly patients have also shown safety and efficacy of both AstraZeneca and Pfizer COVID-19 vaccines [ 16 ].…”

Médecine de Catastrophe

“…Toute décision prise doit tenir compte de la balance bénéfice-risque qui est largement en faveur de tous les vaccins disponibles à ce jour. Leur efficacité, comme l'ont montré les recherches menées tant en Europe qu'aux Etats-Unis, est, par définition, supérieure à cinquante pour cent 34 . En conséquence, le vaccin d'AstraZeneca a été stigmatisé et des patients qui ne savent rien du plus simple calcul risque-bénéfice réclament maintenant le droit de choisir leurs vaccins 35 .…”