Unvaccinated adults who have had the virus are at risk of reinfection, C.D.C. Says
According to a small study that assessed the likelihood of re-infection, unvaccinated people who have had Covid-19 are more than twice as likely to be re-infected as those who test positive and maintain their natural immunity with a vaccine have strengthened.
The study, published Friday by the Centers for Disease Control and Prevention, looked at the risk of reinfection in May and June in hundreds of Kentucky residents who tested positive for the virus in 2020.
Those who weren't vaccinated this year were 2.34 times more likely to get reinfection than those who received their vaccinations. The study suggests that for those who survived infection, the addition of a vaccine offered better protection than the natural immunity created by their original battle with the virus alone.
Although the study looked at only a small number of people in Kentucky, it appears to disprove the argument made by one of its US Senators from his home state, Rand Paul, who has repeatedly claimed that vaccination for people like him who had the virus is unnecessary and developed immunity.
Dr. Rochelle P. Walensky, the director of the C.D.C., said the data reinforces the importance of vaccination, even for those who have already had the virus.
"If you have ever had Covid-19, please get vaccinated anyway," said Dr. Walensky on Friday. "The vaccine is the best way to protect yourself and others around you, especially as the more contagious Delta variant is spreading across the country."
The study's authors warned that not much is known about how long natural immunity to the virus lasts, and that genome sequencing was not performed to confirm that the reinfections were not just a flare-up of the remains of the subjects' original infections .
The C.D.C. and the Biden government has campaigned aggressively to increase vaccinations as the number of cases and hospitalizations has risen sharply in the last month, largely due to the Delta variant and particularly in regions of the country where vaccination rates are low.
According to a New York Times database, the seven-day average of daily new infections in the US was 100,200, above 100,000 for the first time since mid-February. The country recorded 106,723 new cases on Friday.
Another study published on Friday reported that vaccinations drastically reduced hospital admissions for Covid in the elderly in February, March and April. The study looked at data from 7,280 patients from a Covid hospitalization monitoring network and used government records to determine their vaccination status. The vast majority of hospital patients were not or only partially vaccinated; only 5 percent were fully vaccinated.
Although vaccination did not completely eliminate infection, the risk of hospitalization was significantly lower for people who were fully vaccinated. Among those 65 to 74, Pfizer-BioNTech and Moderna vaccines reduced the risk of hospitalization related to Covid by 96 percent, and Johnson & Johnson's single-dose vaccine reduced hospital admissions by 84 percent. In people age 75 and older, the Pfizer vaccine reduced hospital admissions by 91 percent; the Moderna vaccine by 96 percent; and the Johnson & Johnson vaccine by 85 percent.
