Pfizer’s Covid-19 vaccine prevents symptomatic cases of the virus, but it is unclear whether the vaccine prevents transmission of the disease, the United States Food and Drug Administration (FDA) published in a report .
The conclusion highlights a big question mark about vaccine candidates that lingers ahead of an ambitious US launch. Out of millions of injections: How effective will they be in stopping the spread of the coronavirus at the population level.
The answer to that question has important implications for the continued use of public health measures, including face masks and social distancing, even among those who have been immunized.
Prevent or not transmission
Because injections from Pfizer and its German partner Biontech prevent symptomatic cases of Covid-19, their widespread use could prevent transmission of the virus, according to the FDA staff report.
But if the vaccine doesn’t work as well for infections that lack symptoms, those cases “in combination with less mask use and social distancing could result in significant ongoing transmission,” according to the FDA report.
The FDA report was issued ahead of a Thursday meeting of the agency’s outside advisers, whose deliberations will inform whether the vaccine is licensed for use in the United States.
Pfizer expects to report data on whether or not its vaccine stops transmission of the virus in the first quarter of 2021, Chief Executive Officer Albert Bourla said Tuesday at a press conference held by the International Federation of Pharmaceutical Manufacturers and Associations.