A very important study from Denmark published yesterday in the Lancet on 4 million people focused on reinfection of sars-cov-2.
The protection rate for those who have been infected is 80% for adult, and 47% for those > 65 in age.
It means there are 20% and 50% chance of reinfection in adult and older, respectively.
What could be the possible explanation? Immune response differences, CD4, B cells, and TH17 efficacy.
Do we have to reoptimize vaccine guidelines for whom have been previously infected?
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)00575-4/fulltext
The virus is changing and this statistics are not valid for variants.
It is health risk group. There are more health risk group, but this does not mean anything you can catch covid at an early stage.
Have look at this study of SARS-CoV-2 reinfection in Denmark (published in Lancet) among people having a previous COVID-19 based on PCR testing. The reinfection rate is more common in older people compared to young. However, protection against repeat infection was 80·5% up to 6 months after initial SARS-CoV-2 PCR positivity.
Assessment of protection against reinfection with SARS-CoV-2 among 4 million PCR-tested individuals in Denmark in 2020: a population -level observational study
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)00575-4/fulltext
Immunosenescence as the root cause of older people at increased risk of COVID-19 infection, reinfection, outcome, and response to vaccination
It is well known that older people have immunosenescence that predisposes older adults not only to SARS-COV-2 infection, but also reinfection and poor outcomes. Even the vaccines have poor response in the older people. Strategies are being developed how to tackle Immunosenescence to reduce infection risk and improve response to COVID-19 vaccine (1-4).
1. Article Immunosenescence exacerbates the COVID-19
2. Article Aging immunity may exacerbate COVID-19
3. Article SARS-CoV-2, immunosenescence and inflammaging: partners in t...
4. Article Tackling immunosenescence to improve COVID-19 outcomes and v...
I also recommend this recently published paper, that it may answer some of the worrisome questions in the context of SARS-CoV-2 immunity and reinfection.
Durability of immunity to SARS-CoV-2 and other respiratory viruses: Trends in Microbiology (cell.com)
https://doi.org/10.1016/j.tim.2021.03.016
Reinfection after recovery from COVID-19 infection is rare (SIREN Study)
In a UK study (1), patients with documented previous COVID-19 had a median protection of 7 months after initial infection. 155 reinfections were reported in a cohort of 8278 participants who were health care workers (1.87 %).
1. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)00675-9/fulltext