Fact check: Scientists do not yet know whether the COVID-19 vaccine reduces transmission of the virus

A Facebook post, shared hundreds of times since Jan. 15, claims that the COVID-19 vaccine does not prevent transmission of the disease, meaning vaccinated people will effectively become “silent spreaders”. It uses this as an argument against introducing health passports. This claim, however, lacks evidence.

Reuters Fact Check. REUTERS

The post reads: “So what’s the point in vaccine ‘health passports’ if the vaccines don’t even stop transmission? So the vaccinated are going to be the ‘silent-spreaders’ Putting un-vaccinated at risk. #quarantinethevaccinated.” (here).

There have been varying reports in British media about the possibility of vaccine passports and the development of technology that would allow them (, here , here). However, the UK’s Minister for COVID Vaccine Deployment Nadhim Zahawi wrote on Twitter on Jan. 12: “We have no plans to introduce vaccine passports”. He added: “No one has been given or will be required to have a vaccine passport” (here).

Meanwhile, there is currently no conclusive evidence to claim the COVID-19 vaccine stops people spreading the virus that causes the disease – nor is there for the opposite. Early findings from Oxford/AstraZeneca revealed its vaccine could have some effect on transmitting the virus (here), while similar results have also been reported by Pfizer/BioNTech (here).

Scientists do not yet know whether COVID-19 vaccinations will reduce transmission because this was not tested in the trials (here, here). Instead, they found candidate vaccines were able to prevent symptomatic and severe effects of COVID-19 (here), meaning future research would need to take this further (here). For instance, it would need to look deeper into how the vaccine works in the body – whether it prevents an individual getting infected altogether, or whether it simply stops a person becoming sick. With the latter, this could mean the virus continues to replicate in the nose and throat, and is still able to spread (here).

As a result of this lack of information, governments and experts have openly stressed the need to follow social distancing and mask requirements even after being fully vaccinated (here, here, here).


Missing context. There is no conclusive evidence to claim COVID-19 vaccines do not prevent people spreading the disease. Scientists are not yet sure of how the vaccine affects transmission – and this is currently undergoing research. People are still required to follow restrictions even after vaccination to account for this uncertainty.

Read more about our work to fact-check social media posts here .