On the morning of the 26th of last month, citizens wait to be tested for COVID-19 at the screening clinic at the Songpa-gu Public Health Center in Seoul. Provided by Yonhap News
The new coronavirus infection (COVID-19, Corona 19) vaccine is effective in preventing the spread of Corona 19, but the effect does not last long, research results have come out.
A joint research team, including the British Ministry of Health and Social Welfare (DHSC) and Oxford University, found that people vaccinated against COVID-19 on the 29th of last month were less likely to transmit the virus to those around them when they were infected with the delta mutation than those who were not vaccinated. He said that the effect would go away.
The research team analyzed the data of 95,716 COVID-19 confirmed cases and 139,164 close contacts from January to August this year. In July and September, a team of researchers from the National Center for Infectious Diseases in Singapore and Imperial College London in the UK, respectively, published a study result that people vaccinated against COVID-19 were less likely to spread the virus ejected from the nasal passages even if they were infected with the delta mutation. This is the first time that the effectiveness of preventing the spread of COVID-19 has been confirmed.
As a result of the research team’s analysis, the COVID-19 vaccine was effective in preventing transmission. However, the effect of blocking the propagation of the delta mutation was only half the effect on the alpha mutation. In addition, even after three months of vaccination, the effect was reduced to a negligible level. For example, a person who received the AstraZeneca vaccine two weeks after receiving the AstraZeneca vaccine had a 57% chance of passing it on to others if they were infected, but the chance of transmission rose to 67% for those who had been vaccinated three months later. This is similar to the probability that an unvaccinated person will transmit the virus. For Pfizer-BioNtech vaccinees, the chance of transmitting the delta mutation immediately after vaccination was 42%, but after three months it increased to 58%.
David Eyre, a professor of big data at Oxford University in the UK, said, “It explains why the spread of COVID-19 continues even after a large-scale vaccination is done.
The research results were published on the 29th of September on ‘medRxiv’, a pre-publication site for medical thesis.