This question appears to have been answered in correspondence in the New England Journal of Medicine May 5 by Abu-Raddad and others.
Qatar launched a mass immunisation campaign with the Pfizer vaccine on December 21, 2020. As of March 31, 2020, a total of 385,853 persons had received at least one vaccine dose and 265,410 had completed the two doses.
This vaccination scale up occurred whilst Qatar was undergoing its second and third waves of SARS-CoV-2 infection. These waves have been triggered by the B.1.1.7 variant (the so called UK variant) which started in mid-January 2021, and the B.1.351 variant (the so called South African variant).
Genomic sequencing from February 23 through to March 18 indicated that 50% of cases of COVID-19 in Qatar were caused by the B.1.351, the South African variant and 44.5% were caused by the B.1.1.7, the UK variant. Nearly all cases where the virus was sequenced after March 7 indicated that they were caused by either.
The study authors used data on vaccination, PCR testing and clinical characteristics from the National, federated COVID-19 database, which had captured all SARS-CoV-2 related data since the start of the epidemic. They found that the Pfizer vaccine was 90% effective against the SARS-CoV-2 B.1.1.7 UK variant and 75% effective against the B.1.351 South African variant 14 days after the second dose.
A separate cohort analysis compared the incidence of infection in vaccinated persons and in a national cohort who were SARS-CoV-2 antibody negative also supported this finding with an estimated vaccine effectiveness of 87% against the UK variant and 72% against the South African variant. Vaccine effectiveness against severe, critical or fatal SARS-CoV-2 infection from infection with any variant was 97%.
A further study published in the Journal of American Medical Association suggested that the Pfizer vaccine was associated with a 93% lower incidence of symptomatic SARS-CoV-2 infection and an 86% lower incidence of asymptomatic infection more than seven days after the second dose. This was a retrospective cohort of healthcare workers who were studied in Israel.
These studies therefore provide optimistic encouragement that vaccination, certainly by the Pfizer vaccine is effective in controlling symptoms and transmission.
LGP, the leading London doctors’ clinic, commends the Government on its vaccination programme and urges all those applicable to undergo vaccination.
Dr Paul Ettlinger
Founder, The London General Practice