Seroprevalence higher in girls, but third COVID wave unlikely to affect children more, finds AIIMS serosurvey

Contrary to popular belief, it’s unlikely that any future third wave by prevailing COVID-19 variant would disproportionately affect children two years or older, a seroprevalence study has concluded. The study, which compared the COVID-19 sero-positivity rate between children and adults from five locations in four states found a seroprevalence of  55.7 percent in those aged less than 18 (two to 17 years) age group and 63.5 percent in the 18 years and above age group. The SARS-CoV-2 sero-positivity rate among children was high and were comparable to the adult population, the study said. According to the study, published on pre-print server medRxiv, the current findings are based on midterm analysis of data collected from 4,509 participants in four states between 15 March 2021 and 10 June 2021, a period that largely covers the second wave of COVID-19. Of the total participants, a total of 700 participants belonged to the  2-17 year age group, while the remaining from the 18 years and the above age group. In the younger population (2-17 year) group, 92 participants were from Delhi urban resettlement colony, 189 from Delhi rural (villages in Faridabad district under Delhi NCR), 165 from Bhubaneswar rural, 146 from Gorakhpur rural and 108 from Agartala rural area. Seroprevalence higher among girl children The showed also found that seroprevalence in children was slightly more among female participants compared to male (58.6 percent versus 53.0 percent), however, there was no statistically significant difference in sero-positivity between male and female, the study noted. The study, however, said that this “may be a chance finding” due to a small number of data available at the time of midterm analysis. Among the 700 children aged 2-17 years who were part of the serosurvey, 362 (51.7 percent) were male. The number of participants in the aged 2-4 years were 33 (4.8 percent), 5-9 years 153 (21.8 percent), and 10-17 years 512 (73.1 percent). “The higher seropositivity rate in children aged 10-17 years may be reflective of their higher mobility and independence compared to the younger children,” it said. Further, children aged 2-4 years and 5-9 year had almost identical sero-positivity rate (42.4 percent and 43.8 percent) which was lower than the rate observed for children aged 10-17 years (60.3 percent), the study noted. Within the rural sites, children had slightly lower sero-positivity compared to adults, the study said, however, this differential prevalence was not observed in the urban site. What do the findings say about Delhi? “It was found that in resettlement colonies in South Delhi’s urban areas which have a very congested population had a very high (highest reported yet in any sero-assessment) seroprevalence of 74.7 percent,” Dr Puneet Misra, professor of Community Medicine at AIIMS, New Delhi, who led the survey told ANI. Even before the second wave, children below the age of 18 in South Delhi had as much seroprevalence (73.9 percent) as the below 18 years (74.8 percent). “These areas in Delhi and NCR (Faridabad) may have higher seroprevalence after the intense second wave. Probably, these levels of seroprevalence may be protective against any ‘Third wave’,” Dr Misra said. “In congested Urban areas of Delhi, since children already have high seroprevalence, opening schools, may after all not be a very risky proposition. During the second wave, the NCR region of Faridabad (rural area) has a seroprevalence of 59.3 percent (almost equal in both age groups), could be considered high compared to previous national surveys,” the survey said. Chances of herd immunity high in Gorakhpur rural areas The survey said that COVID-19 mostly affected the rural areas in Gorakhpur, which means the chances of herd immunity in these areas is high. While Gorakhpur Rural has a very high seroprevalence of 87.9 percent, the seroprevalence was 80.16 percent in the young group (2-18 years), it was 90.3 percent in the above 18 years group. These levels are likely to ward off the “third wave”, the survey said. According to the survey, the findings from Delhi and Uttar Pradesh partially explain the accelerated peaks and precipitous decline in COVID-19 cases in both states. Among rural areas, seroprevalence least in Agartala Among the five locations that were studied as part of the survey, the Agartala Rural site had the least seroprevalence of 51.9 percent, probably because it also included some tribal population which generally have lower mobility resulting in lower vulnerability to COVID19 infection, ANI reported. Overall, more than half (62.3 percent) of the rural population surveyed showed evidence of past infection. Irrespective of the age groups, rural sites had lower sero-positivity compared to the urban site (Delhi), the study said. The study and was based on interim data from research based on WHO Unity protocol by WHO and AIIMS. It was published in the preprint server medRxiv and was not peer-reviewed. A further study will include a total of 10,000 participants from five states. More results are expected in the next two-three months, ANI said.