Washington – A new study shows the Delta coronavirus (COVID-19) variant produced similar amounts of virus in vaccinated and unvaccinated people if they get infected – illustrating a key motivation behind the federal guidance that now recommends most fully vaccinated Americans wear masks indoors.
Experts say that vaccination makes it less likely that you’ll catch COVID-19 in the first place – but for those who do, this data suggests they could have a similar tendency to spread it as unvaccinated folks.
“High viral loads suggest an increased risk of transmission and raised concern that, unlike with other variants, vaccinated people infected with Delta can transmit the virus,” Dr Rochelle Walensky, director of the US Centres for Disease Control and Prevention, said in a statement Friday.
The study, published by CDC Friday, describes 469 Massachusetts residents who were infected in a July outbreak in Barnstable County, which includes the summer vacation destination Provincetown. No deaths were reported among them.
About 74 per cent – or 346 cases – had been fully vaccinated. Of those cases, 79 per cent reported symptoms. Genetically sequenced cases revealed the Delta variant as the main culprit.
The researchers found evidence that viral loads were similar among 127 fully vaccinated people and 84 others who were unvaccinated, partially vaccinated or whose vaccination status was unknown. Viral load is a proxy for how likely someone might be to transmit the virus to others.
On Tuesday, Walensky previewed these findings while unveiling guidance that people in areas with “high” or “substantial” COVID-19 transmission should resume wearing masks indoors. Over 75 per cent of the US population live in these areas.
The finding that the Delta variant resulted in similar viral loads “was a pivotal discovery leading to CDC’s updated mask recommendation”, Walensky said Friday.
“The masking recommendation was updated to ensure the vaccinated public would not unknowingly transmit virus to others, including their unvaccinated or immunocompromised loved ones.”
(CNN)
