Kids as likely as adults to have asymptomatic Covid

Men, along with the elderly and those with comorbid conditions, are more likely to show symptoms when infected with Covid-19, while the risk of asymptomatic infection among children and young adults did not vary, shows a new study that analysed data from Madurai published in the journal Lancet Infectious Diseases.

The study, which analysed surveillance data of over 440,000 samples that underwent RT-PCR tests for Covid-19 in Tamil Nadu’s Madurai, is one of the first to categorically differentiate the outcomes of symptomatic or asymptomatic infection among Covid-19 cases in India. It analysed risk factors for infection (symptomatic and asymptomatic) and mortality, and probed the completeness of epidemiological reporting in the area.

A group of researchers, led by Ramanan Laxminarayan, director of the Washington-based Centre for Disease Dynamics, Economics and Policy (CDDEP), also found that only 1.4% of the region’s infections could be detected by surveillance, according to data from seroprevalence studies.

One of the key findings of the study, “SARS-CoV-2 infection and mortality during the first epidemic wave in Madurai, south India: a prospective, active surveillance study”, was that there was an equal risk of asymptomatic infection among children, teenagers, as there was in working-age adults – lending support to the argument for the vaccination of children, particularly keeping in mind that governments are currently considering reopening of schools.

The authors had previously published one of the world’s largest Covid-19 contact-tracing studies in the journal Science in 2020, which found that a tenth of all infected patients become “superspreaders” and account for 60% of new infections, while 70% of infected patients do not pass the disease to anyone else.

They said their new findings suggest there are higher chances of symptomatic infection among men and older age groups, and among those who suffer from comorbid conditions such as diabetes, hypertension and respiratory disorders — stressing on the need for early and targeted vaccination of these groups.

In a total sample size of 440,253, men constituted 59% of all infections, but accounted for 62.2% of total symptomatic cases. Similarly, while patients with comorbidities accounted for a little over a quarter (26.8%) of all confirmed infections, they were responsible for nearly a third (31.2%) of all symptomatic cases, according to their findings.

“I don’t think we have had evidence that the elderly with co-morbidities face greater risk for symptomatic infection. This indicates that our limited vaccines should be targeted towards the highest risk age groups rather than at those who are at low risk even of infection,” said Laxminarayan, the study’s lead author.

Laxminarayan, however, stressed that while the epidemiological reporting from their area of analysis (Madurai) was better than what was the national average, there was still a massive proportion of cases that appear to have evaded detection.

“Based on the seroprevalence studies, only 1.4% of infections were ascertained by surveillance. Only 11% of deaths among individuals aged at least 15 years and older, which would be expected based on seroprevalence in Madurai and IFR estimates from other settings, ascertained by surveillance,” the study said. A June-July serosurvey by ICMR across the country showed that on average around 3% of all people exposed to Sars-Cov-2 were detected as confirmed cases across the country.

“The epidemiological reporting, while more complete than other places we have studied still appears to miss a number of cases. Given the resources at the disposal of the health system at large, this is about the best that any district in India could attain and many are far away from that goal,” Laxminarayan said.

“We also find equal risk of asymptomatic infection among the younger age groups but there is evidence from other studies that shows that those with symptomatic infections are more likely to transmit. So here again, I would argue for focusing on higher risk populations of those in older age groups and those in younger ages with comorbidities since the risk of symptomatic infections seems to be greatest here,” he said.