COVID-19: Moderna's chief medical officer warns that a vaccine does not prevent transmission of virus

Laboratory technician Sendy Puerto processes blood samples from participants in clinical trials of Moderna's coronavirus vaccine in September 2020 in Miami, Florida.

Moderna's chief medical officer, Tal Zaks, said on HBO that the public should not ‘over-interpret’ the results of vaccine trials and assume that life could return to normal after vaccination. Tal Zaks warned that the trial results show that the vaccine can only prevent a person from getting sick or ‘severely sick’ from Covid-19. However, the results do not show that the vaccine prevents transmission of the virus.

A vaccine does not stop transmission of virus

Tal Zaks said:

They do not show that they prevent you from potentially carrying this virus transiently and infecting others. When we start the deployment of this vaccine we will not have sufficient concrete data to prove that this vaccine reduces transmission.

Although he believes, on the basis of the scientific evidence, that it is likely that the vaccine will prevent transmission, there is still no solid proof of this. He said:

I think it's important that we don't change behaviour solely on the basis of vaccination.

1 in 3 vaccines proved to be effective

Moderna's Covid-19 vaccine is one of three vaccines that have been shown to be effective in trials. The company said its vaccine is 94.5% effective in protecting people against Covid-19.

Moncef Slaoui, the head of Operation Warp Speed, the White House program to develop and administer the vaccine, said Sunday that the company will apply to the Food and Drug Administration (FDA) for emergency use authorisation for its Covid-19 vaccine before the end of November.

Pfizer, which has developed another vaccine, applied to the FDA on Friday for emergency approval. On Monday, AstraZeneca and Oxford University also said their vaccine was effective against Covid-19.

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