Thursday, January 14, 2021

UK PHE: Results From the SIREN Study On COVID Reinfection


Durable, or at least prolonged, immunity to the COVID pandemic virus - acquired either through natural infection or (preferably) a vaccine - remains the biggest obstacle to ending this global crisis, and the world returning to some semblance of normalcy.  

But we've already seen evidence of a small number of reinfections (see here, here, here, and here), and some studies have suggested that acquired immunity may begin to wane within a few months of recovery (see REACT Study: Coronavirus Antibody Prevalence Falling in England).

There are also new questions being raised about some of the emerging variants - particularly those carrying the E484K mutation - which have been linked to reduced antibody recognition, and which may be better able to reinfect someone (see PrePrint: Genomic Evidence of a Sars-Cov-2 Reinfection Case With E484K Spike Mutation in Brazil).

With the caveat that continued evolution of the SARS-CoV-2 virus can change the picture over time, we've preliminary results from the SIREN study tracking potential reinfection among a large cohort of healthcare workers in the UK, that provides a modicum of reassurance. 
Post infection immunity appears to provide 83% protection against reinfection for at least 5 months, although they warn that some of those infected during the first wave may be vulnerable to reinfection now. 

They also report that those who are reinfected appear more likely to be asymptomatic, which would put them at risk of spreading the virus unknowingly.  Therefore, it is important for everyone to follow the social distancing recommendations, even if they have been previously infected. 

The Preprint hasn't shown up on MedRxiv as of this writing, but should later today. In the meantime we've this press release from the UK's PHE, along with some expert reaction from the Science Media Centre. 

Study finds past coronavirus (COVID-19) infection provides some immunity for at least 5 months, but people may still carry and transmit the virus.

Published 14 January 2021
From:Public Health England

People infected with COVID-19 in the past are likely to be protected against reinfection for several months, a Public Health England (PHE) study has found, although experts cautioned those with immunity may still be able carry the virus in their nose and throat and therefore have a risk of transmitting to others.

PHE has been regularly testing tens of thousands of health care workers across the UK since June for new COVID-19 infections as well as the presence of antibodies, which suggest people have been infected before.

SIREN study leaders are clear this first report provides no evidence towards the antibody or other immune responses from COVID-19 vaccines, nor should any conclusions to be drawn on their effectiveness. The SIREN study will consider vaccine responses later this year.

PHE scientists working on the study have concluded naturally acquired immunity as a result of past infections provide 83% protection against reinfection, compared to people who have not had the disease before. This appears to last at least for 5 months from first becoming sick.

While the SIREN study will continue to assess whether protection may last for longer, this means people who contracted the disease in the first wave may now be vulnerable to catching it again.

Between 18 June and 24 November, scientists detected 44 potential reinfections (2 ‘probable’ and 42 ‘possible’ reinfections) out of 6,614 participants who had tested positive for antibodies. This represents an 83% rate of protection from reinfection.

PHE also warned that although those with antibodies have some protection from becoming ill with COVID-19 themselves, early evidence from the next stage of the study suggests that some of these individuals carry high levels of virus and could continue to transmit the virus to others.

It is therefore crucial that everyone continues to follow the rules and stays at home, even if they have previously had COVID-19, to prevent spreading the virus to others. Remember to wash hands regularly, wear face coverings and make space from others to help reduce the likelihood of passing on the virus.

It is vital that, with cases at their highest level to date and the R number above 1 across the country, people do everything that they can to avoid the risk of transmitting the virus to other people.

Professor Susan Hopkins, Senior Medical Advisor at Public Health England and the SIREN study lead 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. Crucially, we believe people may still be able to pass the virus on.
  • This means even if you believe you already had the disease and are protected, you can be reassured it is highly unlikely you will develop severe infections but there is still a risk that you could acquire an infection and transmit to others. Now more than ever it is vital we all stay at home to protect our health service and save lives.
  • We are immensely grateful to our colleagues in the NHS for giving up their time to volunteer, and whose continued participation at a time of great stress is making this research possible.
(Continue . . . )

You can read a variety of expert reactions on the Science Media Centre website at the following link.

JANUARY 14, 2021
expert reaction to a preprint from the SIREN study looking at SARS-CoV-2 infection rates in antibody positive healthcare workers

A preprint, unpublished non-peer reviewed work, from the SIREN (Sarscov2 Immunity & REinfection EvaluatioN) study compares SARS-CoV-2 infection rates in antibody positive and antibody negative healthcare workers.

This Roundup accompanied an SMC Briefing.