The rate of re-infection of the novel coronavirus infection disease (COVID-19) is increasing across the country. According to the Korea Centers for Disease Control and Prevention on the 23rd, the re-infection rate reaches about 10% in the number of confirmed patients during the week from November 13 to 19. Vaccination against mutations is proving to be effective in preventing reinfection, but studies on the risk of death or seriousness during reinfection are insufficient. The results of domestic and foreign studies on the risk of death and severe re-infection are mixed.
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Re-infection refers to a case in which a positive result was confirmed as a result of a gene amplification (PCR) test or a rapid antigen test for experts after 45 days of the initial confirmation date, regardless of the presence or absence of symptoms. Overseas, there are also reports that the re-infection rate has exceeded 15%. It is predicted that the re-infection rate could be higher in Korea.
BA.5, a sub-system of omicron mutations with a strong tendency to avoid immunity generated by existing infections or vaccines, has become the dominant species, and the number of re-infection cases is increasing as the vaccination rate decreases. The domestic inoculation rate of the bivalent vaccine, which is effective in BA.5, is less than 10%. BA.5 As the effect of the vaccine that was vaccinated before the epidemic gradually decreases, re-infection increases.
Experts stress that the risk of long-term aftereffects increases during re-infection, and that it is important to lower the rate of re-infection through the vaccine's infection prevention effect.
In fact, the effect of preventing reinfection of vaccines is also proven. Denmark's National Serum Research Institute released an analysis in the international journal Floss Medicine on the 22nd (local time) that vaccination has at least 64% and up to 94% of re-infection prevention effects. It was found to have a higher preventive effect than natural immunity obtained from infection. "Vaccines provide practical protection against reinfection," the research team said. "Vaccination is also important for people with natural immunity."
There are mixed studies on the severity of re-infection fatalities
Research results are still insufficient for the fatality rate of re-infection or the risk of hospitalization due to severity. There is also a lack of analysis that the vaccine showed an effect on the risk of hospitalization due to death or severe infection. However, considering the effects of vaccines so far, the general view is that vaccines will have similar effects on re-infection, but opinions are divided as research is insufficient.
A research team at Washington University in St. Louis, USA, released a study in the international journal Nature Medicine on the 10th (local time) that analyzed 6 million data, including infected and re-infected people, collected over the past two years. It is a reversal of the conventional wisdom that the symptoms are light even if infected because the re-infected person has existing immunity.
The research team analyzed that the risk of hospitalization as well as death was about three times higher during re-infection. Analysts say that the risk of Longcovid was also high. For example, the re-infected person was three times more likely to develop heart disease and about 60% more likely to develop neurological disease. This study has a limitation in that most of the samples are male and there are many cases of underlying diseases in old age. However, the research team stressed that the general public should not underestimate re-infection.
In Korea, the opposite analysis results came out. On the 17th, the Central Disease Control Headquarters (CDC) analyzed 24,421,951 people infected with COVID-19 once until the 5th since the COVID-19 epidemic began in January 2020, of which 27,584 died, with a fatality rate of 0.11%. The number of re-infected people was 627,900, of which 523 were killed. The fatality rate is 0.08 percent. It is 0.03 percentage points lower than a single infected person.
However, the fatality rate of the third infected person was 0.43%. It is four times the number of people infected once and five times the number of people infected again. There are only 1,853 samples, but experts believe that in the case of high-risk groups, the risk increases if the infection is repeated. In fact, most of the high-risk elderly people are 5 people aged 60 to 74 and 2 people aged 75 or older who lost their lives due to three infections. Baek Kyung-ran, head of the Korea Centers for Disease Control and Prevention, said, "There is not enough immunity to spend this winter safely," adding, "We are conducting additional vaccinations for adults over the age of 18 in winter." "The elderly with a high risk of seriousness and death must participate in the vaccination," he said.
Writer: Yeyoung Jeon