Coronavirus re-infections raise concerns about immunity

Worldwide there have been over 25 million cases of Covid-19, and there have been three confirmed cases of people getting re-infected with the disease. That amounts to less than 1 in 8 million chances of getting reinfected. Those numbers are in align with other viral diseases. There is no such thing as perfect immunity, whether from recovering from the disease, or from a vaccination, but an immunity of over 99% is pretty good.

It is also important not to down play the importance of the fact that these reinfections are important because they were foretold months ago.

It is the opposite, occasional reinfections have been foretold just because that is the norm for every other infectious disease, so they are just what is expected. A growing number, specially with frequent complications in absence of immune troubles, is the one that would raise an alarm.

Studies in the US by the CDC have shown that there is a three month period after infection where covid-19 antibodies are still detected. After that the CDC stated that reinfection is possible. Which shows the flaws in your last statement.

It is already well known from the other highly pathogenic coronavirus infections that immunity is not solely dependent on antibodies since reactive memory cells can mediate long term protection. Reinfection is possible not because of low level antibodies (which is something much more commonly observed than reinfection) but because the huge number of patients makes it statistically impossible not to see some.

In more simple terms, we know antibody levels are not perfectly correlated with protection, so we cannot predict if a patient is at risk of reinfection just because the titers drop.

Given that there is still so much unknown about covid-19 and its affect on the human body it is extremely important to continue to use every precaution to prevent the spread even if you have had the disease due to the fact that humans don't have any kind of immunity to covid-19 before or after contracting it.

This does not contradict what I wrote, and it is not exactly true, studies have demonstrated cross-reactivity from the cellular component of immunity even from uninfected patients. So humans obviously have immunity after contracting the disease (else nobody would recover) but not only that, people have some kind of immunity even before getting the disease, apparently thanks to the exposure to related low-pathogenic coronaviruses.

Yes, it is still possible that people can get the disease a second time or even transmit it after recovering, but the evidence at this point indicates it is not likely at all, and that herd immunity can be achieved even with this happening sporadically for a small number of patients.

virusrex It is good and fine to be attentive and search for cases of reinfection, but over reacting and giving those cases an exaggerated meaning is not something that should be done.

It is also important not to down play the importance of the fact that these reinfections are important because they were foretold months ago. Studies in the US by the CDC have shown that there is a three month period after infection where covid-19 antibodies are still detected. After that the CDC stated that reinfection is possible. Which shows the flaws in your last statement.

virusrex For all practical purposes this would still make the developing of herd immunity possible, be it with natural infections or vaccines.

Given that there is still so much unknown about covid-19 and its affect on the human body it is extremely important to continue to use every precaution to prevent the spread even if you have had the disease due to the fact that humans don't have any kind of immunity to covid-19 before or after contracting it.

It is good and fine to be attentive and search for cases of reinfection, but over reacting and giving those cases an exaggerated meaning is not something that should be done.

For every virus in the world there are cases where people can get reinfected, that includes those that give "life long immunity", it would be extremely strange that at 8 months of having the pandemic not a single case was found; for now the situation is as expected.

RNA viruses change all the time, even inside the same patient, the genetic sequence you find on the patient on the first day of fever and on the last can be very different, that still does not mean the virus can easily avoid the immune system by mutating. Many vaccines against RNA viruses are effective and give long lasting immunity even with constant mutations of the virus.

It is important also to consider that even if immunity is not perfect and people can get occasionally a second infection it is still very likely the second infection to be much milder and even course without any important shedding of viruses. For all practical purposes this would still make the developing of herd immunity possible, be it with natural infections or vaccines.