People with some COVID-19 immunity may still transmit virus

People with some COVID-19 immunity may still transmit virus
© iStock-VioletaStoimenova

A new study has found that a past coronavirus infection provides some immunity for at least five months, but the virus still may be passed on to others.

The SIREN (SARS-CoV-2 Immunity and Reinfection EvaluatioN) study, carried out by Public Health England (PHE), has shown that people who contract COVID-19 are likely to have protection from reinfection for several months, but that they may still be able to carry the virus and transmit it to others.

The study has been testing for the presence of antibodies in tens of thousands of healthcare workers since June. Leaders of the study are clear it provides no evidence towards the antibody or other immune responses from COVID-19 vaccines and will consider vaccine responses later this year.

Reinfection and immunity

According to the findings, prior COVID-19 infection can provide 83% protection against reinfection, compared to people who have not had the disease before, which appears to last for around at least five months from first becoming sick.

Between 18 June and 24 November, scientists detected 44 potential reinfections out of 6,614 participants who had tested positive for antibodies, representing an 83% rate of protection from reinfection.

PHE also warned that early evidence from the next stage of the study suggests that some of individuals carry high levels of the virus after gaining temporary immunity and could transmit the virus to others – making it vital to continue following social distancing rules and government guidelines.

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.”

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