Live Science: AstraZeneca COVID-19 vaccine can reduce the risk of virus transmission

Live Science: AstraZeneca COVID-19 vaccine can reduce the risk of virus transmission.   According to the Live Science website, the early data of the new coronavirus pneumonia vaccine between AstraZeneca and the University of Oxford shows that the vaccine reduces the risk of becoming severe after infection and mortality, and can also reduce the risk of virus transmission. This is the first report on vaccines to contain the risk of virus transmission.

COVID-19 virus infection can lead to COVID-19 pneumonia or asymptomatic infection. Although it is less harmful to themselves, asymptomatic infections may still spread the virus and cause others to get sick. Researchers at the University of Oxford conducted weekly virus tests on vaccine trial participants and found that after the participants received a dose of the vaccine, the proportion of positive results dropped by about 67%. This means that vaccination can not only prevent disease after infection, but also reduce the risk of transmission caused by asymptomatic infection. This report has been published in the preprint of The Lancet without peer review.

In contrast, other vaccine studies previously released mainly focus on the comparison of the number of patients with symptoms after infection, and the vaccine efficiency is derived from this, rather than data on people infected with the virus. We know that asymptomatic infected people may transmit the virus, so previous studies cannot assess the risk of virus transmission after vaccination.

The author points out that the decline in the proportion of positives after vaccination is of great significance. Assuming that vaccines cannot reduce the risk of asymptomatic infection, vaccination will only convert the originally severe cases into mild cases and mild cases into asymptomatic infections, but it has no effect on the overall positive rate and the risk of transmission. The decline in the positive test rate confirms that the vaccine can prevent asymptomatic infections.

On the other hand, the results of the AstraZeneca vaccine in preventing severe infection and the risk of death showed that 22 days after a single dose of vaccination, the vaccine has an effective rate of 76% in preventing symptomatic infections. The time of the second vaccination is very important. Less than six weeks after the first vaccination, the second vaccination has an effective rate of 54.9%, while the effective rate of vaccination is 82.4% at intervals of 12 weeks or longer.

This result proves that the important factor that affects vaccine efficacy is the interval of vaccination, not the dose of vaccination. The United Kingdom was the first country to promote single-dose vaccination to expand coverage and postponed the second dose of vaccine to 12 weeks later. Although some experts believe that delaying dose interval vaccination will increase the risk of virus mutation, this does not seem to be the case.

At present, AstraZeneca has obtained emergency approval in the UK, and about 10 million people have been vaccinated. The UK has also approved the launch of Moderna and plans to start vaccination in the spring.

(source:internet, reference only)

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