When the first cases of covid-19 appeared in the world, no one was sure how long the immunity given by the virus would last. Would it be permanent, as in the case of measles, or short-lived, as in other coronaviruses that infect humans?
More than two years after a pandemic, we already know the answer: many people caught covid more than once. Sars-CoV-2 re-infection is becoming more common. However, by 2021 they were much lower. “The average duration of natural protection provided by infections caused by Delta variants has been about three months. That is, a person infected with the delta could ‘relax’ for a while, knowing that they would be protected against further infections during that period. “said Dr. Denise Garrett, an epidemiologist.
With the Omikron variant and the emergence of its sub-variants, this scenario changed. “We are increasing the number of re-infections and reducing the interval between them. Re-infections are reported for up to 20 days,” says Dr. Garrett.
A team of scientists at Weill Cornell Medicine in Qatar estimated that an earlier variant of Sars-CoV-2, such as an alpha and delta infection, was about 90% effective in preventing further infection in people with a diagnosis. at least 90 days.
After the appearance of the omicron, according to the study, a pre-virus infection offered 56% protection against another infection. This is because the virus underwent many mutations in the cutting-edge protein, as the new versions became more transmissible and were able to escape the acquired immunity.
There are other factors that are responsible for the current large number of viral infections. We know that the immunity provided by a vaccine or a previous infection decreases over time, so the more months after the vaccine or the first infection, the greater the risk of contracting Sars-CoV-2.
The high circulation of the virus also contributes to re-infections, as it is easier to find at a time when new cases are increasing and states and municipalities have calmed down preventive measures.
But all is not bad news. After a first infection, the body tends to fight another infection more effectively because it “remembers” how the immune system’s cells, such as T and B lymphocytes, need to deal with the virus. Thus, a new infection is usually milder than the previous one.
The same is true for those who have not been infected with the virus but have been vaccinated against the disease. People who are vaccinated can get Sars-CoV-2, but the infection is usually less severe and shorter. “Although it can also be re-infected in people who are vaccinated, it is less common in people who are not vaccinated. Therefore, it is essential to take 3 doses of the vaccine program, even if they are already infected,” said Dr. Garrett.
Those who became vaccinated and became infected develop what experts call “hybrid immunity,” which is the combined protection of existing antibodies produced by the vaccine with natural antibodies caused by an infection.
However, hybrid immunity also does not guarantee that a person will not contract another infection, as the protection changes from one individual to another and decreases over time.
So it doesn’t make sense to want to contract a virus to develop immunity, because it doesn’t last long. In addition, covid can cause long-lasting symptoms. There is still no conclusive study on the percentage of people who develop persistent symptoms after being infected with Sars-CoV-2, but the U.S. Centers for Disease Control and Prevention (CDC) estimates that 1 in 5 people may experience symptoms such as fatigue. difficulty concentrating, loss of smell, among other things, in periods of more than a month.
The best way to get immunity to serious cases of the disease, therefore, is to take the recommended three doses and a booster vaccine, as indicated. The use of masks in enclosed spaces and crowded spaces and the maintenance of ventilated spaces provide additional layers of protection to be used during periods of high virus circulation, such as the current one.