Covid-19 vaccines do offer some protection against transmission and infection

An Instagram post includes a video of presenter and author Neil Oliver on GB News in which he suggests the government knows that Covid-19 vaccines don’t reduce the risk of transmission or infection from the virus. 

During the clip, Mr Oliver references a Sky News interview with Boris Johnson from 22 October and claims: “He [Boris Johnson] was on Sky News this week and acknowledged that while the vaccine offers a level of protection against illness and death, it doesn't protect you against catching the disease and it doesn't protect you against passing it on. 

“Those were his exact words. Surely that sentence right there means vaccine passports would be meaningless and pointless.”

Mr Johnson didn’t use exactly those words but Mr Oliver’s re-telling is broadly accurate.  However, Downing Street confirmed to Full Fact that what Mr Oliver inferred from the interview is not correct. There is also evidence that suggests vaccination does have an effect on transmission and infection rates. 

During the interview in question, Mr Johnson was discussing booster vaccine uptake and said: “The double vaccination provides a lot of protection against serious illness and death but it doesn’t protect you against catching the disease and it doesn’t protect you against passing it on.”

In the video on Instagram, Mr Oliver then goes on to say: “The virus, assuming our Prime Minister’s statement can be trusted, will continue to be spread among the population. Knowing that someone has been vaccinated will make no difference as to whether or not you might catch Covid from them or whether you might pass Covid on. 

“The inference to be drawn from Mr Johnson’s words is that the virus will continue to pass between vaccinated and unvaccinated alike.”

Downing Street confirmed that Mr Johnson was referring to the fact it’s still possible to catch the virus after two doses of vaccine, not that vaccines had no impact on case numbers. 

Evidence also shows that vaccination lowers both the risk of transmission and infection from Covid-19. 

At the end of August, the Scientific Advisory Group for Emergencies (SAGE) gave a consensus view on the protection the Covid-19 vaccines offered against infection. 

It said that the protection from the Delta variant infection was 40% after one dose of the AstraZeneca vaccine and 65% after two doses; for the Pfizer vaccine the estimates were 55% and 75% and the Moderna results 75% and 85% respectively (although SAGE noted the statistical confidence for all of these results was low).

An editorial published in September by the scientific journal Cell  referenced data from Scotland which found the Pfizer vaccine was 79% effective at preventing  infections caused by the Delta variant while the AstraZeneca vaccine was 60% effective after two doses. 

The paper also stated that recent data from England showed both these vaccines “remain highly protective against any infection similar to that seen with Alpha, including those with high viral load” while data from the United States found that “two doses of mRNA vaccines were 75% effective against infection in early 2021, which declined to 53% when Delta predominated.” 

There is also evidence that vaccines can reduce transmission. In a review of evidence on “Indirect Protection by Reducing Transmission” published in May on behalf of the Infectious Diseases Society of America, researchers found “compelling evidence that SARS-CoV-2 vaccination results in a substantial reduction in transmission risk, although the exact magnitude of overall transmission reduction is yet to be fully characterized.” 

It added: “As a result, the vaccines have much greater potential to decrease population morbidity and mortality than they would in a situation where they only prevented symptomatic disease”.

Dr Peter English, a retired consultant in communicable disease control and former editor of Vaccines in Practice, told Full Fact via the Science Media Centre: “We know that two doses of Covid-19 vaccines reduce your chances of being infected and passing the disease on to others to about 20%. 

“Some would say in response to that "so it doesn't prevent onward transmission" and they'd be right that it doesn't completely prevent this; but it does reduce the chances by about 80%.  So others would say "it does prevent onward transmission [by about 80%]".

However, more recent data suggests that vaccination may not hugely reduce the risk of transmitting the Delta variant within households. A study published in The Lancet Infectious Diseases in October, which measured the likelihood of catching the Delta variant from someone else in your household, found a fully vaccinated individual has a 25% chance of catching the virus from an infected household member, while an unvaccinated person has a 38% chance. 

The study said that, although vaccination reduces the risk of infection with the Delta variant, fully vaccinated individuals who do become infected “can efficiently transmit infection in household settings, including to fully vaccinated contacts”.

Dr English also referenced recent data from Israel that suggests that a third “booster” dose greatly reduces infection and transmission, “over and above the benefit of two doses”.

So while the vaccines don’t offer complete protection from transmission and infection there is significant evidence they produce a significant amount of protection and that the third booster dose may further this.