Receiving two vaccinations against the novel coronavirus helped reduce the probability of secondary infections within households from 37% to 13%, a survey by the western Japan prefecture of Hiroshima has shown.
“It’s difficult to prevent infections among people living together,” Takaji Wakita, head of the National Institute of Infectious Diseases, said. “Still, the survey showed that we can prevent infections to a certain extent by receiving two vaccinations.”
The survey covered the families of 752 people who tested positive for COVID-19 in Hiroshima Prefecture in August. The prefecture analyzed 1,840 family members who live with the patients and were recognized as having come into close contact with them, looking into whether the family members suffered secondary infections and whether they had been vaccinated.
Of 1,357 family members who had not been vaccinated, 511 people, or 37.7%, caught the virus.
On the other hand, of 379 family members who had been inoculated twice, only 51 people, or 13.5%, tested positive for COVID-19. The infection rate stood at 27.9% among those who had been vaccinated once.
Hiroshima Prefecture also surveyed 2,006 COVID-19 patients whose infections were detected in the prefecture between June and August. Of unvaccinated patients age 65 and older, 41.7% developed severe symptoms. The rate of becoming seriously ill was much lower, at 13.2% among those of the same age group who received two vaccinations.
As for patients under age 65, the rate of suffering severe symptoms was also lower among those who had been vaccinated twice, standing at 2.2%, compared with 6.9% among unvaccinated people.
Looking into patients with underlying diseases, those who developed moderate to severe symptoms accounted for 7.2% of unvaccinated people and 1.6% of patients who had been vaccinated.
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