Preliminary findings from a study, entitled ‘SARS-CoV-2 Immunity and Reinfection Evaluation (SIREN)’ and conducted on more than 20,000 health workers in the United Kingdom, has found that the immune response generated from a COVID-19 infection could reduce the risk of re-infection by 83% for at least 5 months. The SIREN lead investigator, Susan Hopkins, suggested that the data even indicates that natural immunity may be as effective as a vaccination. It also suggests that immunity lasts longer than some expectations and that reinfection may not be as common as some people feared. The study has been conducted over a five-month period so far and is still being collected and investigated. With protection against reinfection at an approximate 83%, this does not therefore guarantee that a person will not contract the virus a second time and data is still in the early stages of investigation.
Whilst the study has found that antibody protection could last up to five months after infection, and scientists are still studying these antibodies to see if they will last longer, it did not mean that repeat infections were not possible. Nor did it suggest that these repeat infections did not contribute to the spread of COVID-19. Therefore, vigilance against COVID-19 is still tantamount. According to Nature, the SIREN studies data suggested ‘ that repeat infections are rare — they occurred in fewer than 1% of about 6,600 participants who had already been ill with COVID-19. But the researchers also found that people who become reinfected can carry high levels of the virus in their nose and throat, even when they do not show symptoms. Such viral loads have been associated with a high risk of transmitting the virus to others, said Hopkins.’
Hopkins stated that SIREN is apparently the largest of coronavirus re-infection that regularly screens for asymptomatic infections. These screenings are done every two-four weeks and include blood tests for SARS-CoV-2 antibodies and tests to detect the virus. Over the course of the five month study (so far), 44 possible reinfections were found, and in the group of 14,000 participants who had not previously had SARS-CoV-2, 318 people tested positive for COVID-19.
On The Reinfection Cases, Nature Wrote:
‘Some of the reinfections are still being evaluated, Hopkins said. All 44 are considered ‘possible’ reinfections, and were classified on the basis of PCR tests combined with screening measures to reduce the risk of re-detecting virus from the initial infection. So far, only 2 of these 44 cases have passed more stringent tests to be classified as ‘probable’. The study did not assess whether symptoms were better or worse during the second infection than during the first, but Hopkins notes that only about 30% of the people with possible reinfections reported any symptoms, compared with 78% of participants with first-time infections.’
There is not enough data yet, to identify who may be most at risk of reinfection and the study is intended to last for twelve months to glean a better understanding. Further, the investigation has not concluded how long immunity does last and how well immunity protects against the new variant of COVID-19 (B.1.1.7) in the UK. Whilst scientist suspect that immunity should protect against all variants, it is still under investigation and there is a possibility that immune responses vary depending on the variant it is exposed to.
As stated above, those who are ‘immune’ to the virus still can transmit COVID-19 to other people, therefore it is still of vital importance that people wear masks, wash hands, follow social distancing procedures and stay at home if possible and told to do so. Speaking on the research 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. 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.”