Covid cases slow down in festival season but watch out for Diwali: Experts

Vaccinations and more people having already got the disease may have lowered the count.

The surge in Covid cases this festival season appears to have been rather subdued. Vaccinations and prior Covid infections may have lowered the count. Moreover, India’s overall Covid cases had risen in the same period last year, but been on the wane after the second wave of the pandemic.

National Technical Advisory Group on Immunisation in India chief N K Arora said there were two factors at work. One, a sustained demonstration of discipline by citizens. Two, widespread infection by the Delta variant.

“Discipline is of core importance. Even if 25 per cent people in a public place are wearing face masks, the transmission reduces that much. Community has to be appreciated as well,” said Arora.

Echoed Dileep Mavalankar, director, Indian Institute of Public Health. "India's second wave was dominated by the Delta variant. This spread of natural infection led to immunity. Combined with vaccination, it led to resilience during the festival period," he added.

Mavalankar said it is still a mystery why some countries are witnessing a sharp rise in cases, even after relatively high rates of vaccination. "India's early exposure to the Delta variant can offer a possible clue," he said. 

There has been a surge in Israel (65.1 per cent fully vaccinated) and China (70.8 per cent fully vaccinated as on September 18), revealed the figures collated by Our World In Data.

In India, the climb in cases was lower in two of the three major states whose data Business Standard analysed to review the post-festival upshot. Durga Puja in West Bengal (WB) resulted in a fewer cases than last year, as did the Ganpati festival in Maharashtra. Kerala saw cases increase after Onam, aligned with the general rising trend the state has seen after the second wave.

WB had seen 29.3 per cent increase in cases in 2020. The increase in 2021 was 2 per cent. The numbers looked at were the seven-day moving average of confirmed cases a week prior to Mahalaya, signalling the onset of Durga Puja. These were compared with cases seen one week after Vijayadashami, marking the end of Navratri. The symptoms of the disease often take a week to manifest.

A similar exercise was carried out between Ganesh Chaturthi and Anant Chaturdashi in Maharashtra. Cases had risen 65.9 per cent in 2021. Cases actually fell in 2020 by 26.6 per cent. Cases had risen 5.5 per cent around Onam in 2020. It was 26.2 per cent in 2021. Some may be driven by a difference in the proportion of people who had been infected in each state.

A serosurvey that the government carried out in June and July had shown Kerala having the lowest seroprevalence. This would have meant that a marginal share of people had contracted the novel coronavirus earlier than in other states. Maharashtra and WB both had higher seroprevalance.

The serosurvey looks at antibodies through both vaccinations, as well as from having contracted Covid. Kerala had higher vaccination numbers as share of population than either state, revealed an analysis of the data ahead of each of their individual festival seasons. A spike in cases there would also point to fewer people having acquired immunity through contracting it earlier since vaccination should otherwise have resulted in fewer cases. 

On ground, hospitals did not see significant demand for in-patient care. "We had anticipated a surge after Ganesh Chaturthi. Due to the current vaccination drive, people have acquired immunity. Many have developed antibodies. Cases are plateauing," said Dr Harish Chafle, senior consultant, pulmonology and critical care, Global Hospital, in Mumbai's Parel. 

In fact, some hospitals in Mumbai have approached the government to allow them to recast Covid-dedicated wards into non-Covid ones. "The government will assess the situation after Diwali. If there is no spike in cases, this reconversion maybe allowed," said a senior executive of a city-based hospital.

The role that testing plays in this is complex. All three states saw testing numbers drop after the festival season. There was a drop last year as well in Kerala and WB, barring Maharashtra. This may also reflect in fewer people getting infected now since cases have been tailing off.

There was marginal after-festival cases reported this year in the test positivity ratio for both Maharashtra (5.6 percentage point rise in 2020 versus minus 0.5 percentage points this year) and WB (2.3 percentage point rise in 2020 versus 0.6 percentage points in 2021).
 

The test positivity ratio is the number of tests out of 100 which are Covid-positive. Kerala saw an increase (1.25 percentage points in 2020 versus 3.8 percentage points in 2021), in line with the state's trend of absolute increase in case numbers.