The immune system protects us against diseases, this system plays a key role to maintain us healthy because is the responsible of protecting the body from harmful substances, germs, and cell changes. In order to detect these harmful microbes our body exchanges cells and fluids between blood and lymphatic vessels and enables the lymphatic system.
When an unfamiliar substance (antigen) enters the body, the immune system recognizes it as unknown because molecules on the surface of the antigen are different from the ones they identify frequently in our body and the immune system actives some mechanisms, including antibody production, in order to fight against the antigen. Therefore, antibodies, which are also called immunoglobulins, are protective proteins that our immune system produces in response of the presence of an antigen and protects us from them.
There have been some studies that have addressed the possibility of reactivation of the SARS-CoV-2 virus. Although there are still several questions to answer regarding this subject, those studies have demonstrated that there is a real chance to get infected with the virus again, and patients that has been infected in the past could also infect other people during their reinfection. This is due to the fact that the antibodies our body produces doesn’t long for ever as far as we know, and that is the reason why people must take precautions, were a mask and keep physical distancing, even if they have already passed the COVID-19 disease.
It is uncertain if there is a possibility of spreading COVID-19 after vaccination. Scientifics do not know yet the answer to this question and its implications regarding immunity and the effectiveness of the vaccines. Pfizer and Moderna, the companies that have developed two of the vaccines that are available at the moment, have remarked that their vaccines are about 95% effective in preventing people from severe COVID-19 symptoms, which doesn’t mean and there is not clear evidence yet on whether the vaccines stop asymptomatic infection and spread.
According to WHO ‘Herd immunity’, also known as ‘population immunity’, is the indirect protection from an infectious disease that happens when a population is immune either through vaccination or immunity developed through previous infection. However, trying to reach “herd Immunity” by exposing populations to the virus are scientifically unethical, which means it is not a possibility to let COVID-19 spread through populations in order to reach this “group immunity”.
In this sense, vaccines work to help us preparing our system to be ready to create new proteins (antibodies) which will fight against these antigens if they try to enter to our system in the future, and they do it by replicating the same situation that would happen in our system if we were exposed to the virus.
Many people globally have developed immunity to many other seasonal flu strains over time, but due to the fact that COVID-19 is a new virus, natural immunity is not possible, which means that everyone is susceptible to reinfection and to suffer the COVID-19 disease according to the World Health Organization.
Most recent studies have identified thousand of mutations in SARS-CoV-2 samples, but the most of them have not much effect on the virus’s biology.
A vaccine is an agent that replicate a situation of infection inside our body which allows immune system to simulate how they would fight against the virus (producing lymphocytes and antibodies), and they do it in a way they don’t produce the disease. The ideal situation emerges when enough people have been immunized and the virus don’t have eligible hosts, which force it to disappear. When a vaccine is developed, the investigators work in order to build it so that the vaccine effectiveness is not conditionate by the virus’s possible mutations.
Many groups of research have looked at the genetic diversity of the SARS-CoV-2 virus, and they have studied whether the mutations affect the working of the vaccines and last information suggest that as far as we know current vaccines cover existing strains.
As we have mentioned before, there are still undergoing studies aiming the better understanding of the antibody response after infection to SARS-CoV-2. Several of the studies to date show that most people who have been infected with SARS-CoV-2 develop specific antibodies to the virus, however the number of antibodies that each individual produce can vary. Those who experience severe disease usually develop higher levels of antibodies that those with milder disease or asymptomatic infection. According to WHO “Many studies are underway to better understand the levels of antibodies that are needed for protection, and how long these antibodies last.”
The way we can detect and quantify the antibodies our body have produced is thought serological testing (antibodies tests). It is important to have into consideration in this sense that developing antibodies does not mean to be immune to the virus, which lead us to the important need of serology testing, due to the fact that this type of tests allows us to quantify the number of antibodies in our system, and monitories how long these antibodies are effective over time to protect us against the virus.
According to WHO, most people who are infected with COVID-19 develop an immune response within the first few weeks, but we don’t know how strong or lasting that immune response is, or how it differs from one patient to another.
Most people infected with SARS-CoV-2 virus show an antibody response between day 10 and day 21 after infection, however detection in mild cases take longer to show this response (4 or more weeks).
A new study carried out by Rockefeller university in New York (EEUU) concludes that antibodies against SARS-CoV-2 are still able to fight against the virus six months after infection. Additionally, further researchers have showed immunity to the virus can last for at least 8 months and may last longer. Even though, as we stablished before, the detection of antibodies to SARS-CoV-2 does not indicate immunity or protection against COVID-19.