If a person is vaccinated against COVID-19, will they still be able to spread the virus to susceptible people?

An ideal vaccine stops everyone from carrying and passing on the infection as well as protecting them from becoming seriously ill. It is currently unclear whether COVID-19 vaccines only protect against symptomatic and severe disease, or if they can also stop all infection, including asymptomatic infection (i.e. showing no symptoms).

If the vaccine is only able to stop the symptoms of the disease, but unable to stop the virus from infecting us and reproducing, then the virus may still be able to be spread. Even in this case, by reducing the number of people with symptoms will help to reduce spread of the virus because fewer people will be coughing large quantities of virus on others. However, this possible limitation of the vaccine highlights the importance of continuing to follow public health advice such as hand washing and isolating if unwell, even post vaccination. For more information, please click here.

Recently published data from Israel showed that its mass COVID-19 vaccination campaign (using the Pfizer vaccine) was working well with two doses cutting symptomatic cases by 94% across all age groups. Data reported by the CDC in the US has also shown that mRNA COVID-19 vaccines were 90% effective in health care workers against SARS-CoV-2 infection (with and without symptoms).

Last updated: 14 July 2021