The antibodies they produce against the coronavirus during infection only last for a short time.
SARS-CoV-2 is not the first coronavirus to occur in humans. In fact, there are several (relatively innocuous) coronaviruses that are actually constantly active in humans and can cause cold symptoms after infection. The latter viruses are known to be able to infect humans repeatedly and that people are therefore only shortly immune to them after infection. It has already led researchers to fear that infection by SARS-CoV-2 will only lead to short-term immunity.
A new study, conducted among dozens of covid-19 patients, now seems to confirm that. It shows that the antibodies that people produce after they are infected by SARS-CoV-2 decrease quite quickly. According British researchers whose paper, which has yet to undergo peer review.
For their research, the scientists followed 94 people who had been proven to have contracted the coronavirus. Over a period of three months, the scientists looked at how the antibody concentrations developed in the bodies of these (former) corona patients. At the height of the infection, 60% of the individuals studied were found to possess antibodies that could neutralize the virus. A few months after the individuals examined showed the first symptoms, only 16.7 percent of the individuals studied were found to possess potent neutralizing antibodies. And in some people, the neutralizing antibodies were no longer detectable at that point.
The research further indicates that the number of antibodies that people produce is closely related to the severity of the infection. In people who become seriously ill due to the virus, the antibody concentration is higher. In addition, it takes longer for that concentration to return to pre-infection levels.
This research has important implications for vaccine development. For example, it may mean that vaccines aimed at generating neutralizing antibodies should be repeatedly administered to continue to provide protection against SARS-CoV-2.
In addition, the whole idea of group immunity is further called into question. Because group immunity requires people to be immune for a long time. The moment you are immune to a virus, you can no longer be infected by it yourself. And you can no longer pass it on to others. If a large part of the population were immune to SARS-CoV-2, the virus could hardly spread anymore and the people who are not immune to the virus may also be protected. In such a situation, we speak of group immunity. In the case of SARS-CoV-2, group immunity would only be achieved when about 60% of people had the virus.
The new research shows that after infection, humans are only short-term immune to SARS-CoV-2, but it should be noted that the study only looked at one way in which our bodies can deal with SARS-CoV-2, namely antibodies. However, there are other ways in which our bodies can tackle the virus, for example, it can also use T-cells, and researchers at Erasmus MC have previously stated that activating these cells are at least as important as the production of antibodies. In addition, the T cells can play a crucial role in long-term immunity.
What also remains unclear is what exactly the decrease in antibodies means for a possible second infection. It is not very unusual that the concentration of antibodies – and also the concentration of T-cells – eventually decreases again after an infection. But that doesn’t automatically mean that previously infected people would get sick by the disease again. Because these concentrations of antibodies and T-cells can then increase much faster with a second infection, so that the infection is different – milder – the second time. Whether that is also the case with SARS-CoV-2, we do not know. If so, that would be good news for people who have already had the virus. But at the same time it means that they are not really immune to the virus and can (again) spread it during a second infection – even if it is milder.
When it comes to our immunity to SARS-CoV-2, there is still a lot to investigate. And that’s not so crazy either. Because we are dealing here with a virus that was unknown to us until December 2019. And now that the virus has been sweeping the world for some time, we are only able to investigate how our immune system reacts to it in the long term and what implications it has for its control.
Editor-in-chief of the Scientific Origin, Shakes is the swiss-army knife of the Organization. Besides assuring the well-functioning of the magazine, he also covers stories ranging from science to health, to technology, to astronomy, etc… On a typical weekend, you’ll find him enjoying a picnic at a local park or playing soccer with friends.