With the arrival of the first coronavirus vaccines in Italy, many people who have tested positive for the virus are wondering whether or not they can undergo vaccination like others. The topic is still discussed among researchers, but a precautionary approach is prevailing with the advice to vaccinate anyway, albeit with less urgency than those who have never come into contact with the coronavirus.
Generally speaking, a vaccine it serves to develop an immune response against a particular virus or bacterium (pathogen), so that the body learns to recognize it and fight it in the case of subsequent infections. A similar process occurs in the event that you contract a pathogen and recover, but the vaccine does so without getting sick and running the risks of the disease.
The coronavirus vaccines so far authorized in the European Union, that of Pfizer-BioNTech is that of Modern, they achieve this with similar systems. They are based onMessenger RNA, the molecule that encodes and carries the instructions for making proteins. They employ synthetic forms of mRNA – made in the laboratory – that contain instructions for making some coronavirus-specific proteins. In this way the immune system learns to recognize and fight them, but without the risks that would be run in the case of an infection with the actual coronavirus. The knowledge acquired in countering these proteins can then be used by the immune system to counteract any real infection.
To date, we do not know how long the immune system retains information on what it has learned from the vaccine: it is therefore not known how long immunity induced by vaccination lasts. These vaccines have been in circulation in the community for a few weeks, even though they had previously been subjected to clinical tests on tens of thousands of people and lasted several months. We will know more about them later in the year, but we know that they are effective in protecting against the severe symptoms of COVID-19.
In general, when we recover from some viral diseases, such as measles or the mumps (the “mumps”), we develop a long-term immunity that lasts for a lifetime and protects us from subsequent infections. The same result can be obtained with vaccinations, without running the risk of getting sick and having complications (measles has a high lethality among children). However, there are some viral diseases, such as the flu, to which we struggle to produce an immune response that is maintained over the long term. This depends both on how we are made and on the flu viruses that tend to vary over time. In cases like these, getting vaccinated helps the immune system to better deal with any new contacts with particular variants, reducing the risk of getting sick.
At the moment there is no scientific evidence that there are variants of the coronavirus such as to require a vaccination for those who have already suffered an infection, as happens with the flu. The problem is that we don’t know how long acquired immunity lasts and therefore how long the protection lasts for individuals who have already come into contact with the coronavirus. It is not even completely clear whether there are significant differences between those who tested positive, remaining asymptomatic, and those who then developed COVID-19, the actual disease.
If protection for the recovered were to last only a few months, then vaccination would be even more helpful in inducing the immune system to maintain its defenses against the coronavirus. Immunity studies are still ongoing, but there are some elements that suggest that immunity acquired through an infection due to the current coronavirus does not last very long. For this reason, several health institutions also recommend vaccinations to those who have already had a coronavirus infection.
What the institutions say
In Italy, vaccination against coronavirus is on a voluntary basis in any case, but the Italian Medicines Agency recommend to those who have been positive to get vaccinated anyway, even if with less urgency than the others:
Vaccination does not contrast with a previous COVID-19 infection, rather it enhances his immune memory, so no pre-vaccination test is useful. However, those diagnosed with COVID-19 positivity do not need vaccination in the first phase of the vaccination campaign, while it could be considered when obtaining data on the duration of immune protection. However, it is not necessary to undergo diagnostic tests for Covid-19 before accessing the vaccination.
Yes, anyone who has had COVID-19 can be vaccinated.
Several other health authorities agree on this approach, and not only because it could actually improve immune protection in individuals, but also for practical reasons. In a large part of the population, the coronavirus causes no symptoms or causes very mild ones, to the point of not realizing that they have contracted it. There are therefore millions of people who have unknowingly suffered the infection and who have probably developed some immune defenses against the coronavirus.
Banning or advising against vaccination for those who have already had the virus would therefore be very difficult, given that many will turn up to receive the vaccine without knowing whether or not they have been infected in the past. Before undergoing the vaccination, a serological test is not required to detect any infection that occurred previously. It is an approach that is also followed with the vaccines we have been using for some time. For example, often if you are unsure whether you had measles as a child, you are advised to go ahead with the vaccine instead of checking for antibodies through a blood test – it is more practical, direct and inexpensive.
Those who know they have had the coronavirus in recent times could still decide to postpone vaccination for a few months, having acquired natural immunity for a while, reducing the workload for vaccine administration centers and facilitating vaccinations for those who is more exposed. This choice could prove useful in starting mass vaccination campaigns, given that there will be hundreds of thousands of individuals with a recent coronavirus infection potentially less at risk than others.