- A PHE study tracked cases of coronavirus reinfections among healthcare workers
- Just 44 people caught the virus again out of 6,614 previously infected people
- Of the 44 people, just 15 of them developed symptoms, study data reveals
- Experts say previous infection gives 94% protection against symptomatic reinfection and 83% reduced risk for all infections
- However this might not be effective for asymptomatic people
According to an article published in the Daily Mail UK, people previously infected with the coronavirus have more protection against reinfection five months later than people getting the Oxford vaccine, and the same level of immunity that is provided by the Pfizer jab, a Public Health England (PHE) study has found.
What is it?
Data from PHE’s SIREN study, which follows more than 20,000 healthcare workers at more than 100 sites across Britain, looked at how many members of NHS staff in the study group caught the virus more than once.
A total of 6,614 workers were found to have had the virus in early 2020, either through antibody testing, PCR swabs or clinical evaluation based on symptoms.
Just 44 people from this group later tested positive for the coronavirus as a result of reinfection.
PHE scientists say this means previous infection confers 83 per cent protection against reinfection, and also reduces the likelihood of developing symptoms and severe disease.
Data from Public Health England’s SIREN study, which follows more than 20,000 healthcare workers at more than 100 sites across Britain, looked at how many members of NHS staff that caught the virus twice.Just 44 cases of reinfection were seen in group of 6,614 people
T cell immunity to Covid-19 lasts at least six months
Covid-19 patients maintain a form of immunity against the coronavirus for at least six months after infection, a new study shows.
The findings may mean people who have already had the virus are less likely to get reinfected if they come into contact with the virus again.
A group of more than 2,000 people working for Public Health England volunteered to take part in the study and donate blood every month, with the first people recruited in early March, before lockdown was announced.
A total of 100 people tested positive for SARS-CoV-2, the virus which causes Covid-19, but none were hospitalised. More than half (56 per cent) had symptoms.
The study focused on a specific type of immune response, called T cells, which are created by the body following infection. They are different to antibodies but are just as pivotal in fighting disease.
The scientists behind the research call their findings encouraging and are ‘cautiously optimistic’ there is long-lasting and robust immunity following coronavirus infection.
How did they do it?
Researchers gave participants monthly antibody tests as well as weekly PCR swabs to monitor any infections between June and November.
This methodology allowed the researchers to pick up on infected people with symptoms as well as those who were asymptomatic.
How effective is this method?
Professor Susan Hopkins from PHE, lead author of the study, says this method is more stringent than is used in the testing of vaccines, which relies solely on symptomatic cases.
She explained that Pfizer/BioNTech’s efficacy rate of 95 per cent is therefore likely to be inflated as it does not account for asymptomatic infections.
In the PHE study, only 15 people from the group of 44 reinfected individuals developed symptoms.
Take Home Message
Professor Eleanor Riley from the University of Edinburgh, who was not involved with the research, said: ‘The take home message from this study is that a primary infection with SARS-CoV-2 provides at least 94 per cent protection against symptomatic reinfection for at least five months.’
‘This suggests that natural infection provides short term protection against Covid-19 that is very similar to that conferred by vaccination.’
A Robust Protective Effect
Professor Hopkins said in a press conference that the protective effect of previous infection is approximately as robust as that of the Pfizer vaccine and ‘much better’ than the AstraZeneca/Oxford jab, which registered an efficacy rate of 62.1 per cent in participants who received two standard doses.
Researchers from PHE categorised the reinfections as either probable or possible, but are unable to say with certainty due to the fact PCR tests and genome sampling was not widely available during the first wave.
However, the 44 cases (two probable and 42 possible) meet criteria which led to their inclusion in the study, including a positive test for SARS-CoV-2 infection.
What does this mean?
‘The findings will help to give, alongside the vaccine, the ability to slow transmission of the virus,’ Professor Hopkins said.
‘But it is not complete protection and people still need to be careful when out and about and take precautions.’
The Clearest Picture of Antibody Protection
Professor Susan Hopkins from PHE said the protective effect of previous infection is as robust as that of the Pfizer vaccine and ‘much better’ than the Astrazeneca/Oxford jab, which registered an efficacy rate of 62.1 per cent in participants who received two standard doses
The researchers are only able to say the length of time natural immunity lasts for is five months because that was the duration of the study.
Professor Susan Hopkins said: ‘This study has given us the clearest picture to date of the nature of antibody protection against COVID-19 but it is critical people do not misunderstand these early findings.’
‘We now know that most of those who have had the virus, and developed antibodies, are protected from reinfection, but this is not total and we do not yet know how long protection lasts.’
The SIREN trial will continue for 12 months and more data will be released soon which will reveal how the new coronavirus variants have affected reinfection rates and if natural immunity has a time limit.
What about asymptomatic people?
However, in people who were coronavirus positive but asymptomatic the researchers found evidence they had high viral loads, which indicates they would be able to infect other people despite not feeling ill themselves.
But Professor Riley says reinfection is so rare that people who have been previously infected are ‘much less likely to transmit the virus to others’.
‘This is good news in terms of the long term trends of the pandemic. However, asymptomatic reinfections are not zero, so you cannot assume that just because you have had the virus before that you can’t be infectious,’ she says.
These data reinforce the message that, for the time being, everyone should consider themselves to be a potential source of infection for others and should behave accordingly.
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Source : Daily mail
