UK study finds COVID vaccines still effective against Delta variant
- Pfizer/BioNTech and Oxford/AstraZeneca vaccines still offer protection against new infections
- The vaccines are better at preventing severe disease, a scientist said
- The Pfizer/BioNTech vaccine had a 93% efficacy rate against symptomatic infection
A United Kingdom study found that two COVID-19 vaccine doses still remain the most effective way to ensure protection against the Delta variant that was first identified in India. The study conducted by scientists at the University of Oxford involved more than 700,000 randomly selected people from within the community.
“With Delta, Pfizer/BioNTech and Oxford/AstraZeneca vaccines still offer good protection against new infections, but effectiveness is reduced compared with Alpha (first identified in England last year and previously the dominant VOC in the UK),” read the findings of the study.
“Two doses of either vaccine still provided at least the same level of protection as having had COVID-19 before through natural infection; people who had been vaccinated after already being infected with COVID-19 had even more protection than vaccinated individuals who had not had COVID-19 before,” the study said.
The study also confirmed the higher level of infectiousness of the Delta variant as the infection after two vaccine doses had similar peak levels of the virus as compared to those in unvaccinated people. However, with the Alpha variant, peak virus levels in those who were infected after vaccination were much lower.
"The vaccines are better at preventing severe disease and are less effective at preventing transmission,” said Dr Koen Pouwels, one of the lead researchers of the study.
"The fact that you see more viral load (with the Delta variant) hints towards herd immunity being more challenging," he said.
The study also revealed that a single dose of the Moderna vaccine has similar or greater effectiveness against the Delta variant as single doses of the other vaccines.
Also, two doses of Pfizer/BioNTech have greater initial effectiveness against new COVID-19 infections. However, it plummets quicker when compared to two doses of Oxford/AstraZeneca.
“Results suggest that after four to five months, effectiveness of these two vaccines would be similar – however, long-term effects need to be studied,” the study said.
The Pfizer/BioNTech vaccine had a 93% efficacy rate against symptomatic infection two weeks after the second dose as compared to Oxford/AstraZeneca's 71%.
The study also mentioned that the interval between doses does not affect effectiveness in preventing new infections.
The researchers analysed two and a half million test results from 743,526 participants in the UK's COVID-19 household infection survey.