COVID-19 vaccinations reduce risk of reinfection by 50 per cent

Those who have recovered from a coronavirus infection have a 50% lower chance of getting COVID-19 again with severe symptoms than those who have not received the vaccine.

These findings were made public in a study that was published in the medical journal Frontiers in Medicine and was overseen by Lamberto Manzoli, a medical epidemiologist and the director of the University of Bologna’s School of Public Health and Hygiene.

“Our results confirm that, among the recovered, those who have received two or three doses of vaccine have a 50% to 60% lower risk of reinfection than those who are not vaccinated,” explains Professor Manzoli. “Considering that the number of people who recovered is now in the hundreds of millions worldwide, these results appear particularly encouraging and provide strategic information for future pandemic control policies.”

The study was undertaken by gathering and evaluating data from 18 studies that were carried out in various regions of the world and included a sample of altogether 18 million people. It also included researchers from the University of Ferrara and the Sapienza University of Rome. Through a series of analysis of the data gathered, researchers assessed several elements of COVID-19 reinfection. These included variations in the severity and contagiousness of various variants, differences between individuals who received two and three doses of the vaccine, and protection that persisted 12 months after the last infection.

Two key findings were found. One study demonstrates that vaccination reduces the risk of COVID-19 reinfections by half compared to natural immunity alone acquired with a viral recovery.

Moreover, data show that even if a second infection occurs, the likelihood of developing severe symptoms is halved in vaccinated people. Similar levels of protection were observed in people vaccinated with only one dose, even for the Omicron variant and up to 12 months since the last infection.

“It is worth noting that vaccines have reduced a thankfully already low risk: in absolute terms, the number of reinfections may seem worrying, but cases of severe or fatal COVID-19 symptoms among people who have already recovered once are relatively infrequent: less than 1 in 1,000,” adds Manzoli. “These findings can thus be useful for planning specific immunization strategies for people who have already contracted the coronavirus.”