Investigating a population in southern Sweden, a new study has found that a single dose of the vaccine is only about 42% effective in preventing coronavirus disease 2019 (COVID-19). But seven days after the second dose, the vaccine can prevent COVID-19 in 86% of the population.
Of the total of 805,741 study participants, about 3% had been vaccinated by the BNT16b2 mRNA vaccine by 28 February 2021. About 80% of the vaccinated individuals were women, and the median age of the vaccinated set of people was 47 years.
Two weeks after the first dose, the vaccine was only about 42% effective. But it was 86% effective in preventing COVID-19 in people who had no prior infection seven days after the second dose for the period 15-28 February 2021. There was no difference in vaccine effectiveness between males and females.
he study found lower vaccine effectiveness of about 60% within seven days of the second dose.
People who had been infected before showed a 91% vaccine effectiveness. The effectiveness was still high when people had been infected more than three months before vaccination.