Secondary infection refers to the phenomenon that after a certain time span, COVID-19's symptoms reappear, and the amount of virus in the infected person rises again after rehabilitation.
Compared with Yang's recovery, the amount of virus in the second infected person is relatively high, and the time span is longer, generally more than 3 months, but with the increase of infection times, the time span will be shortened.
So compared with the previous strains, is the secondary infection rate caused by Omicron higher? Will the effect of repeated infection be greater?
Conclusion 1: Omicron is more susceptible to secondary infection.
It was found that the secondary infection rate in COVID-19 showed a rising trend. The secondary infection rate of early strain α was 0.57%, the secondary infection rate of δ increased to 65438 0.25%, and the secondary infection rate of Omicron was 5.8 times that of α, reaching 3.365438 0%.
But even so, at least about 85% people will not be infected again.
Conclusion 2: The probability of secondary infection of the same strain is small.
What factors will increase the chance of secondary infection? Related to the first infected strain.
Due to the constant variation of COVID-19, there are some differences between strains of different lineages, and the probability of secondary infection caused by the same strain is small.
According to the data of the National Bureau of Statistics, if the infected person is infected with BA.4/BA.5 for the first time in Omicron, the rate of re-infection with this strain is only 0.7%.
Conclusion 3: The effectiveness of antibody decreases with time.
According to 12 related academic reports, the longer the time from the first infection, the weaker the protective effect of antibodies in the body, and the easier it is for secondary infection to occur.
According to a paper published by the European Center for Disease Control and Prevention in The Lancet in September this year, the protective effect of antibodies in the body was 565,438+0% within three to five months after Omicron infection, but less than 25% after the first infection six months ago.
In addition, compared with α and δ, the degree of antibody protection after Omicron infection decreased even more.
Conclusion 4: Specific occupations are more susceptible to infection.
The risk of secondary infection is also related to occupation.
Medical staff who are often exposed to viruses are more likely to have secondary infections. In the related paper published in The Lancet-Regional Health (Southeast Asia) in August this year, the infection and reinfection density of Indian medical staff (HCW) from 202 1 12 1 to February 25th, 2022 were investigated.
Compared with students and administrative/civilian staff, the risk of secondary infection of doctors is 2.7 1 times, and that of nurses is 2.89 times.
Conclusion 5: Young people are more prone to secondary infection.
From the age point of view, according to eight academic reports, compared with the elderly group, the young group is more likely to be reinfected.
Among patients with secondary infection, 18 ~ 40 years old accounted for the largest proportion, accounting for 5 1. 1%, followed by 18 years old and 4 1 ~ 60 years old, accounting for 23.6% and 20% respectively. The proportion of the elderly is relatively low, with only 3.8% aged 6 1 to 80, while the proportion over 80 is 1.4%.
It should be noted that young people are more prone to secondary infections, not because of physiological reasons, but because of their social activities.
Conclusion 6: Vaccine can effectively reduce the probability of secondary infection.
So, how to reduce the probability of secondary infection?
According to the research of Italian Sacco and other scholars, in Italy, the risk of secondary infection of unvaccinated people is 2.9 times that of vaccinated people.
Moreover, with the increase of the number of inoculation needles, the risk of secondary infection gradually decreases. But at the same time, it should be noted that, consistent with the antibodies in vivo after infection, the effectiveness of vaccines to prevent secondary infection will weaken with time.
Conclusion 7: Severe secondary infection rate decreased.
Compared with the first infection, the severity of diseases caused by the second infection decreased, including hospitalization rate, ICU severity rate and mortality rate.
According to the research published by Cornell University Epidemiology Group in March this year, serious secondary infection is very rare, with only 0. 1% cases showing severe symptoms, and none of them showing critical symptoms.
In addition, the Institute of Health Informatics of University College London pointed out that even for the elderly, the risk of hospitalization caused by secondary infection has been reduced.
According to the paper published in May this year, among the 2,264 residents of the long-term care center in the UK, the risk of reinfection in the hospital is lower than that of the first-time infected patients, which is only 2 1% of the first-time infected patients.
Therefore, for secondary infection, don't worry too much, implement protective measures, including wearing masks, paying attention to hand hygiene and keeping social distance. And actively vaccinate COVID-19 vaccine to reduce the risk of infection.