Why are so many people in England getting reinfected with Covid?

The rise of a variant of Omicron known as BA.2 has been linked to the increase in Covid infections in parts of the UK. What does this mean for reinfections?

Can you get Covid more than once?

Yes. According to the latest weekly report from the UK Health Security Agency, since the beginning of the Pandemic to 20 March this year there have been over one million possible reinfection episodes in England. Since the start of the Pandemic, 8,717 third episodes and 74 fourth episodes have been identified.

Not everyone with Covid takes a test, the figures are likely to be undercount.

The UKHSA data shows that the rate of reinfection shot up towards the end of the year and then fell again.

Why have reinfections become more common?

The protection against catching the virus after a Covid infection fades over time. The data shows that the risk of reinfection is higher in unvaccinated people, while the severity of the previous infections and the level of immune response may also play a role.

The more people who have had Covid, the greater the pool of individuals that could potentially be re-invastated and the less restrictions are needed.

The immunity of the body may hold up better against some variations than others.

When Omicron arrived in the UK at the end of 2021, it was clear that the variant was highly transmissible and could cause serious harm.

Prof Danny Altmann, an immunologist at Imperial College London, said that infections are more frequent and rapid than before.

How likely are you to get BA.2 if you have already had the original Omicron variant?

Although the risk of hospitalisation appears to be no greater than the original Omicron variant, data from the UKHSA suggests that BA.2 is even more transmissible. BA.2 is the most common variant of Covid in the UK.

The ability to evade the body's immune responses seems to be the same between BA.2 and BA.1. The point is highlighted by research from the US, with the authors noting the rise of BA.2 following the surge of BA.1 is probably related to increased transmissibility rather than to enhanced immune escape.

It seems that it is very rare for someone to get BA.2 shortly after an infection with BA.1 is possible.

Both BA.1 and BA.2 are new, and it takes time for reinfections to occur.

We are at the beginning of the 90-day period for possible reinfection with BA.2 following a BA.1 infection, but there are no early indications of a specific reinfection issue with this scenario.

However, drawing on his own research, he sounded a note of caution.

The surprising aspect is that, even compared to expectations from common colds, Omicron seems so poorly immunogenic that it doesn't even stimulate good immunity to itself.