Although the novel coronavirus infection (COVID-19, Corona 19) vaccine is effective in preventing the spread of COVID-19, a study has found that the effect does not last long.
The UK Ministry of Health and Social Welfare (DHSC) and a joint research team at Oxford University found that when people who were vaccinated against COVID-19 on the 29th of last month were infected with the delta mutation, they were less likely to transmit the virus to those around them than those who were not vaccinated. He said that the effect disappeared after passing.
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 later had a 57% chance of passing it on to others if they were infected with the AstraZeneca vaccine. 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 increased to 58% after three months.
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 site for pre-publication of medical papers.
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