BBC News Mundo

The vaccine, produced in Belgium, is a new type of vaccine called RNA, which uses a small fragment of the virus's genetic code to teach the body how to fight COVID-19 and generate immunity.

The rest of the vaccines—including Russia's Sputnik V, which began mass distribution in Moscow, China's Sinovac, the US's Moderna, and the British Oxford-AstraZeneca—remain in the race, and approval for some is expected imminently.

In the United Kingdom, the first to receive the initial dose of the two needed to achieve full immunity are people over 80, frontline healthcare professionals, and nursing home workers.

And while the majority of the population eagerly awaits their turn, some are looking at the vaccine with suspicion due to the unknowns that still remain unanswered.

One of the recurring questions (although not necessarily among those who disagree with vaccination) is what generates a stronger immune response: natural infection or the vaccine?

BBC Mundo spoke with three experts on the subject in search of an answer.

Depending on the case

In short: it's still unknown.

"There are some diseases where the vaccine protects more than the disease, and other cases where the disease provides more protection than the vaccine," Carlos Rodrigo, a vaccinologist and Clinical Director of Pediatrics at the Germans Trias i Pujol Hospital in Barcelona, ​​explains to BBC Mundo.

Rodrigo gives as examples classic diseases such as measles, chickenpox, and mumps, where natural infection provides longer-lasting immunity, and it's normal that once you have had it, you don't get sick again.

In other types of infections, such as those caused by pneumococci or meningococci (two types of bacteria) in children or by the human papillomavirus (HPV)—a group of viruses that can cause warts and several types of cancer—the situation is exactly the opposite.

In the case of HPV, for example, the vaccine generates a more potent immune response than natural immunity, as the latter is particularly weak.

This is because, among other things, the virus employs various tactics to evade the immune system, Maitreyi Shivkumar, professor of molecular biology at the School of Pharmacy at De Montfort University in the United Kingdom, explains to BBC Mundo.

"Many viruses, including HPV, have proteins that block the immune response or simply maintain a low profile to avoid detection."

The vaccine, on the other hand, "contains a high concentration of a single protein—the one that protrudes from the surface of the virus and the one detected by the immune system—in its purest form."

By delivering a large amount of this protein, the response generated is much stronger, Shivkumar points out.

And, in addition, the vaccine allows, "in a way, the immune system not to be distracted by other pieces of the virus (as would occur in a natural infection)," the expert adds, although she clarifies that there are few cases where the immunity generated by the vaccine is greater than that elicited by natural infection.

"Vaccines are generally as good as the infection (in this sense), or they provide sufficient immunity, and that is what we want to achieve."