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24 March 2023
Published online 13 July 2021
Significant waves of infection coinciding with mass vaccination rollouts provide unique insight into vaccine effectiveness against two variants.
A large study of recipients of the Moderna COVID-19 vaccine in Qatar has found it is highly effective against the Alpha and Beta variants of the SARS-CoV-2 virus, which were originally documented in the UK and South Africa respectively.
“This is very good news,” says Laith Abu-Raddad of Weill Cornell Medicine-Qatar, who specializes in healthcare policy and research, emphasising the vaccine’s effectiveness against symptomatic and asymptomatic infections, including severe forms of the disease.
The results add further support for studies indicating the value of the messenger RNA (mRNA) vaccine approach in fighting the pandemic.
mRNA vaccines, which insert into cells the instructions for making a protein to induce immunity, had not been widely available for use on humans prior to the COVID-19 pandemic. The Moderna vaccine is one of only two mRNA vaccines that have been approved so far.
Mass vaccination with the Moderna vaccine in Qatar began in February 2021. This coincided with two significant waves of infection due to the SARS-CoV-2 Alpha and Beta variants. The researchers say this timely combination created “a unique epidemiological opportunity” to assess the real-world effectiveness of the vaccine against infection with recently emerged variants.
They monitored clinical and virus-testing evidence from a sample of 256,037 individuals who received at least one dose of the vaccine and 181,304 who had received two doses.
Vaccination proved ineffective for the first two weeks but then quickly became 88.1% effective at preventing infection with the Alpha variant, rising to almost 100% after the second dose. For the Beta variant the corresponding values were 64.3% effectiveness from two weeks after the first dose and 96.4% after the second.
The reduction in the likelihood of developing severe forms of disease due to any form of COVID-19 was 81.6% and 95.7% after the first and second dose, respectively.
Wafaa El-Sadr, an epidemiologist at Columbia University in New York, who was not involved in the research, says the findings from Qatar are very important and shed light on the crucial question of whether our current vaccine can be protective against new variants of the virus. “The news is quite reassuring,” she adds.
Chemaitelly, H. et al. mRNA-1273 COVID-19 vaccine effectiveness against the B.1.1.7 and B.1.351 variants and severe COVID-19 disease in Qatar. Nat. Med. https://doi.org/10.1038/s41591-021-01446-y (2021).