Once you’ve had both of your doses – and you’re deemed fully vaccinated – what happens next? How much of a risk do you pose to others? And how much risk is there of you still becoming sick with the virus?

The first thing to bear in mind is if you’ve only just had your second dose, you still aren’t fully protected. People are considered fully vaccinated two to three weeks after their second dose, as it takes time for the jab to give protection.  And even then, you can still get Covid-19, but the symptoms should be less severe – you might even get it and not know it (meaning you’re asymptomatic). 

The way to reduce everyone’s risk of coronavirus is to break the chains of transmission and push down the number of cases, says England’s deputy chief medical officer, Jonathan Van-Tam. But we don’t yet know the impact of the vaccines on transmission of the virus. While studies suggest the vaccines can lower transmission to some degree, it’s not entirely clear by how much.

“Even after you have had both doses of the vaccine you may still give Covid to someone else and the chains of transmission will then continue,” Prof Van-Tam explained in an op-ed earlier this year.

If people go about their business like they did in pre-Covid times, it could be problematic for those who aren’t yet vaccinated, those who have only had one dose, or people who are immunocompromised or immunosuppressed. In the latter group, it’s thought Covid vaccination provides a lower level of protection.

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The risk of catching and spreading Covid after vaccination will depend on a number of factors, says Professor Paul Hunter, of the Norwich School of Medicine at University of East Anglia. These include: how much infection there is circulating in the community, how effective the vaccine you had is, how long the immunity lasts after vaccination, and what proportion of infections are new variants with escape mutations.

“If there’s a surge of infections in the community, then even if you’re vaccinated, you’re still more at risk than when case numbers are low,” says Prof Hunter.

Different vaccines have different rates of effectiveness, but all of them have been shown to reduce disease severity, hospitalisation and deaths, which is good news. The Pfizer vaccine’s effectiveness is at least 97% in preventing symptomatic disease, severe/critical disease and death, while the AstraZeneca vaccine has been found to be 76% effective at preventing the virus. 

The Moderna jab – to be rolled out in April – has a vaccine efficacy of 94.5%, meaning it should protect against around nine in 10 cases of Covid-19. All of the jabs require two doses for maximum protection.

The effectiveness of such jabs will vary with the Brazil and South African variants of concern, which are thought to be better at evading the immune system – even after you’ve had the jab.

Results are mixed. One study found the Pfizer vaccine produces an “off the scale” immune response that’s likely to protect against the Brazilian variant of Covid-19. It also suggests people are likely to be protected against the Wuhan and Kent variants following two doses of the vaccine. Other data from Pfizer suggests the vaccine is 100% effective in preventing Covid-19 cases in South Africa, where the other variant of concern hails from.

But the AstraZeneca vaccine has seen less impressive results. One study suggests it had just a 10% efficacy against the South African variant. There are murmurings the jab might work better against the Brazil variant, however.

Like all medicines, no vaccine is 100% effective against Covid-19, so people are advised to still take precautions to avoid infection and to keep cases down. While you might be eager to hug all your relatives and throw wild parties after being jabbed, it’s important to continue to follow national guidance. 

This means practising social distancing, wearing a face mask, washing your hands carefully and frequently, and opening windows to let fresh air in and improve ventilation – especially when restrictions lift, meaning people can socialise indoors.

Prof Hunter urges caution after having the jab. “There remains a risk of further infection and transmission with all vaccines,” he says.

Experts are still learning about Covid-19. The information in this story is what was known or available at the time of publication, but guidance could change as scientists discover more about the virus. To keep up to date with health advice and cases in your area, visit gov.uk/coronavirus and nhs.uk.