Pfizer's oral COVID-19 antiviral was not effective at preventing infection among adults living in the same house as an infected person, according to new trial data.
The interim findings are based on an analysis of nearly 3,000 adults who were household contacts with someone who had recently tested positive for the virus. At the time of enrollment, the participants were asymptomatic and had tested negative. Participants were randomly selected to receive the antiviral Paxlovid or a placebo within 96 hours of the infected contact testing positive. Paxlovid recipients were given the drug for either five or 10 days.
Compared to those who took the placebo, participants who were given Paxlovid for five days were 32 percent less likely to become infected. That rose slightly to 37 percent when the drug was given for 10 days.
The drugmakers said the results were not statistically significant but do not negate strong results supporting Paxlovid's primary use, which is to prevent severe outcomes among those already infected and at high-risk for progressing to severe disease.
"While we are disappointed in the outcome of this particular study, these results do not impact the strong efficacy and safety data we've observed in our earlier trial for the treatment of COVID-19 patients at high risk of developing severe illness, and we are pleased to see the growing global use of Paxlovid in that population," Albert Bourla, Pfizer's CEO, said in an April 29 news release.