Two doses of the Pfizer and AstraZeneca Covid-19 vaccines can reduce transmission of the Delta variant by 65% and 36% respectively, a new UK government-funded study shows.
The FDA has approved a single booster shot of Pfizer’s Covid-19 vaccine for senior citizens aged 65 and older and certain high-risk groups, after previously authorising a third dose in a three-dose primary vaccination series for immunocompromised individuals.
The independent JCVI considers the margin of benefit too small to support universal vaccination of healthy children aged 12 to 15, as Covid-19 infection is asymptomatic or mildly symptomatic in the vast majority of children.
Oxford University’s research found that Pfizer and AstraZeneca vaccine efficacy fell to 78% and 61% respectively within 90 days after the second shot, but the lead scientist says both Covid-19 vaccines are still very effective against Delta overall.
The emergency use authorisation does not include fully vaccinated healthy people as both the Pfizer-BioNTech and the Moderna vaccines have shown to be highly effective at preventing hospitalisation and death in this group.
Prime Minister Prayuth Chan-ocha’s administration has been extensively criticised for failing to secure timely and adequate vaccine supplies, which has complicated plans to vaccinate at least 70% of the country’s 69 million population this year.
An internal CDC document says more breakthrough infections and community spread are expected with the Delta variant despite Covid-19 vaccination, although vaccines prevent more than 90% of severe disease.