20% of coronavirus sick did not develop immunity
Bnei Brak serological survey shows at least 9% of city had COVID- 19
Only 80% of people who tested positive for coronavirus had antibodies to the virus, according to a report published Monday by the Central Bureau of Statistics, the Health Ministry and the Gertner Institute.
The results mean that a percentage of people who develop asymptomatic or even mild cases of the virus could contract it again.
The report was based on a serological survey conducted between June and August in the haredi ( ultra- Orthodox) community of Bnei Brak. The city has had some of the highest rates of infection in the country.
The survey also found that the number of people who tested positive for antibodies increased with the number of sick patients, thought not proportionally.
In June, 2% of the Bnei Brak population tested positive and 6.3% had antibodies. In July 4.1% tested positive and 6.4% had antibodies, and in August 5.6% tested positive and 13.8% had antibodies. On average, at the time that the research concluded, some 9% of the Bnei Brak population were thought to have immunity to coronavirus.
“The infection rate is not nearly enough to assume herd immunity,” said Dr. Boaz Lev, the ombudsman of the medical professions at the Health Ministry. Speaking at a briefing on
Monday, he said that the results show that even in communities where the infection rate was high, social distancing and wearing masks continues to be important.
The researchers said that Bnei Brak likely has a higher level of immunity today, but they could not say how high.
The survey also revealed additional relevant findings, such as people with larger families were more likely to spread the virus to each other. In families of eight people or more with at least one verified patient, 11.2% of members were found to have antibodies, meaning they had contracted the virus. The number in smaller families was only 7.9%.
This also proved true in buildings and communities. The survey showed that people who lived in the same apartment building as someone with coronavirus was more likely to contract the disease than someone who did not – 10.2% of people in buildings with a verified patient had antibodies versus 7.2% within the general population at the time this part of the study was conducted.
The survey divided up Bnei Brak into four districts. There were more people with antibodies in areas with higher populations. At the same time, there were more people with antibodies found in neighborhoods that were more heavily populated with ultra- Orthodox people.
There were also noticeable differences between age groups: Of those aged 7- 14, 8.3% had antibodies, versus those 15- 24 of which 13.8% had antibodies, and those over the age of 60, of which only 5.3% had immunity.
As expected, the rate of infection among children was lower than adults. Also, in line with international research, 12.1% of men developed antibodies, meaning they caught coronavirus, versus 6.2% of women.
Moving forward, the researchers said that they would need to screen the people who showed they had antibodies again to see how long those antibodies last.
Already, explained Prof. Daniel Cohen, acting head of the Tel Aviv University School of Public Health, it is understood that people begin to lose immunity after three or four months – meaning that their immunity weakens. He said it is unclear if it completely goes away.
According to separate research conducted by Gili Regev- Yochay, the director of the Infectious Disease Epidemiology Unit at Sheba Medical Center, Tel Hashomer, only about 2- 3% of people who developed antibodies to the novel coronavirus lost them.
In tests conducted of 300 coronavirus patients, those who were infected with the virus and recovered maintained their immunity, although it may have lessened overtime.
Regev- Yochay said that Sheba has been running a parallel program to the Health Ministry to screen people for antibodies who have either lived with someone who had coronavirus or have had it themselves. If they are found to have immunity, they qualify for the nation’s new program that allows them to receive a “green card” and avoid unnecessary isolation.
Head of Public Health Services Sharon Alroy- Preis said last week that people with proven immunity to the virus will no longer need to enter isolation if they come in contact with a sick person. Also, they will not have to enter isolation if they return to Israel from a red state.
Regev- Yochay explained however that the green card does not last for more than a month or two at which point the patient would need to be retested.
“Our current understanding is that people who do have antibodies are immune,” said Regev- Yochay. “It may be transient but while the antibodies are there, they are very important.”