In a new study, researchers found that the first dose of the Pfizer/BioNTech vaccination is 85% effective against COVID-19 between two and four weeks after inoculation.
The research was conducted by a team at Harvard University and elsewhere.
In the study, the team surveyed healthcare workers at the largest hospital in Israel, which on December 19 launched a mass vaccination campaign.
They found that the vaccine developed by US Pfizer and Germany BioNTech to be 95% effective one week after a second jab.
Some 7,000 of them received the first dose and the rest were not inoculated.
From the group, 170 were diagnosed with COVID-19 after tests carried out only on those showing symptoms or who had been in contact with coronavirus carriers.
About 52% of them were found to have not been vaccinated.
Comparing the two groups, the team found that the vaccine was 47% effective between one and 14 days after inoculation, and the effect rose to 85% after 15 to 28 days.
They say that despite the vaccine is quite effective, researchers still need to study whether fully vaccinated people can transmit the virus to others.
One author of the study is Gili Regev-Yochay from the Department of Epidemiology.
The study is published in the Lancet.
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