Study Suggests Lower Transmission Risk from COVID-19 Reinfection

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Study Suggests Lower Transmission Risk from COVID-19 Reinfection

Study Suggests Lower Transmission Risk from COVID-19 Reinfection

When individuals with a history of COVID-19 are reinfected, there may be a reduced risk of transmitting the virus to others, according to findings compiled by a team from the Japan National Institute of Infectious Diseases and Nagoya University.

The research team revealed that reinfected individuals can rapidly produce immune substances in their bodies that diminish the infectivity of proliferating viruses, making it less likely to transmit the virus to others even when expelled from the body.

Study Suggests Lower Transmission Risk from COVID-19 Reinfection

The correlation between the early production of these immune substances and a shorter virus shedding period was elucidated for the first time through analysis using human samples.

The research team focused on “secretory antibodies,” substances produced on the mucosal surface of the nasal cavity. These antibodies, a type produced by immune cells, efficiently eliminate harmful foreign substances entering the body through the nasal mucosa.

While the passage of the virus through the nasal mucosa was known to have some effect when the virus proliferates in the body of an infected individual and exits, the details were previously unclear.

To investigate, data on 122 individuals infected with the Omicron variant in the country were used to examine the secretion of antibodies and the duration of virus shedding.

The results showed that in individuals who were infected for the first time without vaccination, it took an average of 10.4 days for the secretion of antibodies to exceed a certain level, whereas in reinfection cases, this period was shortened to 5.2 days.

Regarding the duration of shedding infectious viruses, first-time infected individuals took an average of 9 days from infection, while reinfection cases reduced it to 5.9 days.

In contrast, for vaccinated individuals experiencing their first infection, the period for the secretion of antibodies to surpass a certain level was shorter, averaging 8.6 days from infection, compared to those without vaccination for the first infection. However, the shedding period was similar, with an average of 8.4 days.

The research team explained, “Current COVID-19 vaccines are highly effective in preventing severe cases, but reducing the duration of shedding infectious viruses is challenging.

To prepare for the emergence of unknown infectious diseases, developing vaccines that efficiently produce secretory antibodies could help suppress outbreaks early.”

The findings were published on the 19th in the Proceedings of the National Academy of Sciences (PNAS).