WASHINGTON • Three-quarters of people infected with Covid-19 at July public events in a town on Cape Cod in Massachusetts were fully vaccinated, a study by the US Centres for Disease Control and Prevention (CDC) showed.
The study, published on Friday, suggested the Delta variant of the virus was highly contagious. The outbreak occurred in Provincetown on Cape Cod, according to Barnstable County health authorities.
The CDC study found vaccinated individuals had a similar amount of virus presence as the unvaccinated, suggesting that, unlike with other variants, vaccinated people infected with the Delta variant could transmit the virus.
CDC director Rochelle Walensky said this was a "pivotal discovery" leading to CDC's recommendation last week that masks be worn in areas where cases were surging as a precaution against possible transmission by fully vaccinated people.
"The masking recommendation was updated to ensure the vaccinated public would not unknowingly transmit virus to others, including their unvaccinated or immunocompromised loved ones," Dr Walensky said.
The CDC said 469 cases were found among Massachusetts residents from July 3 to 26 related to the Cape Cod outbreak.
Of those, 74 per cent were among fully vaccinated people. The CDC said its study excluded residents of 22 other states. Barnstable County reported that as at Friday, 934 cases in total had been associated with the outbreak.
The CDC said that overall, 79 per cent of the vaccinated individuals who were infected with Covid-19 also reported symptoms such as cough, headache, sore throat and fever. Four had to be hospitalised.
Vaccinated individuals had received one of the three available shots made by Pfizer and BioNTech, Moderna or Johnson & Johnson, the data showed.
The study's authors recommended the local health authorities consider requiring masks in indoor public settings regardless of vaccination status or the number of cases in the community. The CDC said that people with Covid-19 reported having been at densely packed indoor and outdoor events including bars, restaurants, guest houses and rental homes.
Top US infectious disease expert Anthony Fauci said on Friday he hopes regulators could start granting full approval for the Covid-19 vaccines as soon as this month, a move he said could spur unvaccinated Americans to get the shots.
The Pfizer-BioNTech and Moderna two-dose vaccines and Johnson & Johnson's one-dose shot are currently being administered under emergency use authorisation by the US Food and Drug Administration (FDA).
Full approval by the FDA could push more Americans to get the Covid-19 vaccine as it might reduce their fears about the safety of the shot and make local officials more comfortable about implementing vaccine mandates, Dr Fauci, director of the National Institute of Allergy and Infectious Diseases and chief medical adviser to the White House, said in an interview with Reuters.
In addition, formal FDA approval would give physicians the ability to prescribe a third dose of the vaccine to people with weakened immune systems on an off-label basis, Dr Fauci said.
Pfizer and BioNTech, as well as Moderna, have filed with the FDA to ask for full approval for their vaccines. Johnson & Johnson has not yet requested full approval for its Covid-19 shot.
"Given what we've been through now and the number of months that have gone by since the (emergency use authorisation), I would hope that within the very reasonable period of time in the future we'll see that. I hope as we get into the middle of August, that we're almost there," Dr Fauci said.
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