Do I need a COVID vaccine if I’ve had COVID?

October 7, 2021

Thanks to your contributions to the ZOE COVID Study app, we  know that having two or more doses of a COVID-19 vaccine cuts the chances of catching COVID-19, reduces the likelihood of being seriously ill or hospitalised if you do get it, and also halves the risk of developing Long COVID

Even so, some people still prefer to rely on natural immunity, instead of getting vaccinated. However, our latest analysis shows that a previous COVID-19 infection and being double vaccinated gives longer-lasting protection than vaccination or natural immunity alone. 

Does COVID-19 infection give better protection?

Together with our research colleagues at King’s College London, we analysed data from more than a million regular UK contributors to the ZOE COVID Study app, which enables people to log their vaccination status and COVID test results along with daily health reports.

We defined six groups of people, according to whether they were double vaccinated with either the Pfizer or AstraZeneca vaccines or were unvaccinated, and whether they had previously tested positive for COVID-19. 

We then looked at how many people in each of these groups reported testing for positive COVID-19 during the UK Delta wave from May to September 2021, and calculated their level of protection against the virus.

We found that two doses of the AstraZeneca vaccine gave 71% protection against infection, increasing to 90% for people who had previously tested positive for COVID-19.

Two doses of the Pfizer vaccine provided 87% protection, which went up to 95% for people who had already been infected with the virus.

By contrast, having had COVID-19 without being vaccinated only gave 65% protection against catching it again.


Should I get vaccinated if I’ve already had COVID?

Our findings show that COVID-19 infection before double vaccination provides much greater protection, which supports the call for everyone to get vaccinated even if they’ve already had COVID. 

Reassuringly, those who were infected in the first wave back in Spring 2020, we also found that the protection from a previous COVID-19 infection didn’t wane, up to 450 days after the infection, independent of whether the person was vaccinated or not. 

Professor Tim Spector, lead scientist on the ZOE COVID Study app, says: “Regardless of which vaccine is administered, this latest research shows that having a natural COVID-19 infection before being fully vaccinated does mean greater protection. This is really positive news for overall immunity levels in the UK, and means that large numbers of people will have effective and long lasting protection from COVID-19.”

Do I need a booster jab if I’ve already had COVID?

Booster jabs are now rolling out across the UK for people at the most risk from COVID-19.

But given that being fully vaccinated on top of a previous COVID infection provides such strong protection, should we be already offering people in this group a booster jab? 

Tim says, “ If you’re not yet eligible for a booster, but have had a previous infection and two vaccines, I wouldn't be too worried as your protection will be very high. It’s important we focus on the number of high-risk people who remain unvaccinated, which is still too high, as we fall behind the rest of Europe, slowing our progress in reducing rates of infection and bringing the pandemic to an end.”

How can I help COVID vaccine research?

It’s vital that we continue to gather as much data as possible on the spread of COVID and the impact of vaccination. 

You can now log any COVID vaccine in the ZOE COVID Study app, including boosters and vaccines received as part of a clinical trial. And we’ll soon be adding the ability to log vaccines for other diseases including flu. 

To get involved, simply download the ZOE COVID Study app and start logging daily health reports as well as your vaccinations. It only takes a minute, but you’ll be contributing to life-saving research. 

Stay safe and keep logging.

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