Should those recovered from Covid-19 be vaccinated?
Yes, because to date we do not know how long the protection of the immune system lasts after Covid-19 infection (asymptomatic or symptomatic) and moreover it is likely that the answer is not unique from person to person. The amount of antibodies after infection is generally not comparable to the higher one obtained after immunization: by vaccinating even the recovered, the enhancement and optimization of the immune response is achieved. Mario Clerici, full professor of Immunology at the University of Milan and scientific director of the Don Gnocchi Foundation.
When should they do it?
The new guidelines published by the Istituto Superiore di Sanit establish thatthose who have recovered for more than six months should take both doses, while a single dose is recommended after at least three months from the documented infection and preferably within six months. Immunosuppressed are an exception and, even if recovered from Covid-19, they must be vaccinated as soon as possible with a double dose.
Why only one dose?
The single dose works as a booster and stimulates a high amount of antibodies. The recommendation is based on publications cited by the ISS in which it was found that in people with previous Sars-CoV-2 infection the immune response evoked by the first dose of mRNA vaccine is robust and comparable and even higher than that obtained with two doses in subjects seronegative. Furthermore, according to very preliminary data, it is conceivable that the immune response at the second dose in those who have already been infected may be irrelevant or counterproductive. The data refer to mRNA vaccines and according to the ISS there are no differences for other types of products. The choice of a single dose in the first six months of the infection – however, Clerici points out – derives more from the fact that there is shortage of vaccines ed right at this moment to favor those who are still susceptible. Even those recovered should still follow the classic double dose protocol and will be able to do so once the product is more available, in a few months.
Is there a recommended vaccine for those who have had Covid-19?
No, we don’t know. There is no clinical trial that suggests a type of vaccine better than the other for the vaccinated – adds the immunologist – but since we are talking about single doses, for common sense one could think of Johnson & Johnson. However, it would be a choice that does not derive from clinical practice.
How long does the immunity from a previous infection last?
The ISS document reports a multicenter study of 6,600 UK healthcare professionals that assessed the risk of reinfection: The duration of the protective effect of the infection has a median of 5 months. However, other studies report immunological memory data even longer than eight months.
What happens if I find out with a serological test that I no longer have antibodies despite a recent illness?
The fact that there is a weak or absent antibody response after months – the immunologist explains – does not mean that there is no protection. The short-term immune response mediated by antibody-producing B cells, and what a serological test detects. There are also memory T cells, which stimulate the production of antibodies when there is contact with the virus. Studies tell us that humans and monkeys infected with Sars-CoV-2, despite not having B cells, have T lymphocytes. The problem is that we can’t go looking for memory cells.
Is there no test to measure T lymphocytes?
No, this is not possible. a very complex procedure, only possible in highly specialized research facilities, used in some studies to measure the duration of memory protection explains Clerici.
Is it useful to do the serological test to ascertain if you have already been affected by the virus?
The ISS says it is not indicated. There is no reason – confirms the professor – because even if you have had an infection, even without symptoms, the indication is to get vaccinated. Constraining the vaccine to the presence or absence of antibodies makes no sense.
It is not dangerous to do the double dose if you have already had the infection, perhaps without knowing it?
No, in the extreme, adverse reactions such as fever, chills and muscle aches, weakness, longer lasting headaches can occur – concludes the immunologist -. an expected response because it is going to stimulate an immune response that is already there, but none of the side effects have been so serious as to suggest not taking the second dose.
March 17, 2021 (change March 17, 2021 | 21:57)