How soon after Covid can you catch it again? Reinfection and immunity explained - how long can symptoms last

Covid infections have hit the highest level since mid-April as the Omicron BA.5 variant continues to spread.

The highly infectious strain is now the dominant variant of coronavirus in the UK and has been found to be more transmissible than previous strains.

A total of 3.8 million people were estimated to have Covid in the UK in the week to 14 July, up 7% from 3.5 million in the previous seven days, according to the Office for National Statistics (ONS).

Kara Steel, ONS senior statistician for the Covid-19 infection survey, said: “Infections have, overall, continued to increase in England, reaching similar levels to those seen in April during the BA.2 wave.

“However, we are seeing some uncertain trends in the latest data across the other UK countries, some English regions and among some age groups.

“It is too early to say if this most recent wave is starting to peak, but we will continue to closely monitor the data.”

The figures come after a study found that two-thirds of people recently infected with the Omicron variant say they have had coronavirus before.

The findings from a large, continuing study, React, swab-tested more than two million volunteers in England and found that two out of every three (65%) of the infected volunteers said they had already previously tested positive for Covid.

The study found that healthcare workers, households with children, or homes with a lot of people appear to be more likely to catch the virus for a second time.

But how soon after having Covid can you catch it again? Here’s what you need to know about reinfection, how long infection can last, when you are most contagious.

How soon after Covid can you get it again?

It is possible to be infected with Covid more than once as immunity against the virus will wane over time.

The Omicron variant in particular is thought to be more than five times more likely to cause reinfection than the Delta variant, according to an Imperial College London report, which could be due to the large amount of mutations in the spike protein.

As Covid is still a relatively new virus, it is still unclear how long immunity can last, but a recent Public Health England (PHE) study found that more people who have had coronavirus are protected from catching it again for at least five months.

However, this was before the Omicron variant arrived in the UK. New data now suggests that many people who were infected with a previous variant are now going on to catch Omicron.

Vaccine research does swho that two vaccine doses plus a booster are still protecting against serious disease, even among those unlucky enought to have the virus more than once.

Evidence also suggests that each new infection causes milder illness.

Residual signs of Covid infection can still appear on a PCR test for up to three months after, even if a person is not displaying any symptoms.

As such, the UK Health Security Agency (UKHSA) currently only considers a person to have been reinfected with the virus if they get a positive PCR test result after 90 days or more from their initial illness, or a prior test date.

What factors can influence reinfection?

Studies suggest that those who are unvaccinated are at greater risk of catching Covid-19 again, as vaccination provides longer protection than natural infection

A US study found that people who have not been vaccinated are 2.34 times more likely to be reinfected with coronavirus than those who have had the jab.

Data from the Office for National Statistics (ONS) also found that people are more likely to be reinfected if they received their second vaccine dose more than 90 days ago, compared to those who had it between 14 and 89 days ago.

By comparison, those who had not had any jabs were three times more likely to be reinfected than those who got their second dose 14 to 89 days ago.

Viral load is another factor that can influence reinfection, with people more likely to get Covid-19 again if they had a lower load at their initial infection, according to the ONS.

Studies suggest that people who only have only mild symptoms, or none at all, may not develop as much of a strong immune response as those who have more severe disease.

However, every reinfection from Covid-19 tends to be associated with milder disease than the previous illness.

How long can Covid symptoms last?

It can take between five and six days on average for symptoms of Covid to appear, although some people can start to feel unwell from one to 14 days after infection.

The length of time it takes for a negative test result to appear after infection will depend on how severe symptoms are.

Studies suggest that PCR tests start to detect the virus around one to three days before symptoms start, which is when the viral load will be highest. After this point, the amount of virus in the body gradually declines until it can no longer be detected by PCR.

Asymptomatic people can typically test positive for one to 14 days, while those with mild-to moderate disease will often continue to test positive for seven days or more.

Those who have symptoms should generally only feel unwell for around five days on average, after which the effects should start to clear.