On August 24 the news of a person reinfected with coronavirus surprised the whole world and upset those who are basing their strategy on supposed immunity that is obtained when passing the disease. It was a 33-year-old from Hong Kong who had been discharged in April but who, four months later, tested positive for coronavirus again when he returned to his country from Spain. It was the first documented case of reinfection by Covid-19.

Report four patients reinfected with Covid-19 in Spain, one of them serious in the ICU

Since then, several European countries – such as the Netherlands or Belgium – have reported cases of reinfected patients. In Spain, this Monday four cases of Covid reinfection were documented in Catalonia, one of them, in addition, in quite serious condition.

There is still much to know about the coronavirus, which is why new uncertainties continue to appear every day. Even so, the Ministry of Health launched a message of calm this Monday, ensuring that this type of cases of people recontacted are “extremely exceptional “, taking into account the total number of cases in the world. The Secretary of State for Health, Silvia Calzón, said this, explaining that they are “following and applying the protocols” to analyze this “exceptional situation in the natural course of infection.”

Statements that are in line with what the World Health Organization (WHO) affirmed after the Hong Kong case was made public. “We get anecdotal reports from time to time of people getting tested negative and then positive, but it has not been clear so far if this is a problem with the test itself or if there were people who actually got infected a second time.” said WHO spokeswoman Margaret Harris, emphasizing that, even so, the possible reinfections that are being talked about “they represent a very, very low figure”

“The cases of reinfection, taking into account the number of people who have been infected, are very low,” reiterates scientist Laura Lechuga, who is currently leading a new project in development to create a test that could detect Covid-19 in 30 minutes. Although she admits that the scientific community follows these cases with concern, she assures that they are still exceptions, for which she considers that,. “Until we have more numbers, it is too early to decide if it is a serious problem or not”.

Re-infection is common in respiratory viruses, such as the common flu. “There are many viruses that if you suffer them once, you are immunized forever, but in the case of respiratory viruses it is common to get reinfected. This is what happens with the flu, which mutates a little and you can get infected again “, says the researcher at the Catalan Institute of Nanoscience and Nanotechnology, pointing out that, even so, more data is still needed from Covid-19 and more time to be able to specify.

So, in the hypothetical case that the reinfection rate increased Could it have implications, for example, in the development of future vaccines or even in herd immunity? The scientist assures that it would affect both matters. “We are very far from group immunity”, he recalls, adding that it can only be obtained when vaccines begin to be available and, “among those who are vaccinated and those who have already passed it, because perhaps we will get closer to that group immunity “.

“It may happen like the common flu, that vaccines are effective for a year and a dose will have to be given again the following year”

But he does not consider that it may have too many effects on the development of vaccines, since the virus does not seem to mutate too much; at least not as much as HIV, whose multiple mutations complicated finding a vaccine. “What happens to us with the common flu can happen, that vaccines are effective for a year or a little more, and a dose has to be given again the following year”, he explains, pointing out that it may be that the immunity that is generated in individuals does not have that memory.

The human immune system is quite complex. According to the researcher, there are dtypes of immunity: the fast, which are the antibodies, the immunoglobins that we immediately generate to fight the virus; and the long-term immunity of T cells, which creates a kind of “memory” in our immune system in which the virus has attacked, and, “if it re-enters, it begins to make immunoglobins quickly to kill it before it spreads.”

“It may be that the immunity that is generated in individuals does not have that memory and that, therefore, people have to be vaccinated every year or every two years,” he explains. By now, both different immunities are known to be activating in patients, “But it’s all speculation … it’s the bad thing about something new, right? That as long as you don’t have the data, you don’t know at all”, Laura Lechuga concludes.