How Covid-19 waves are turning into ripples; dip in latest surge fastest

The fourth time that the 10,000-mark was breached was in April 2023. The latest spike lasted 7 days-the shortest of the four.

Sachin P MampattaSohini Das Mumbai

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Rising Covid-19 cases have never petered out faster than in the latest surge.
The 7-day rolling average num­ber of daily cases rose to more than 10,000 on April 20 and had decl­ined below that level by April 27. The 7-day rolling average has been considered to smoothen out fluctuations in testing of samples and rep­orting of results. The period sp­ent above the 10,000-mark in te­rms of daily cases in this latest ins­tance was a week. It had ranged between two months to over a year in previous instances of cases rising.

The first time that daily cases rose above 10,000 was in June 2020. The number stayed above that level for 530 days, including both the first and second waves. The decline after the first wave peaked in September 2020 still saw the daily 7-day moving average stay above 10,000 cases at the nadir in February 2021. The second wave peaked with around 400,000 cases in May. The gradual decline after the second wave eventually led to cases falling below 10,000 in November 2021.
 N K Arora, head, Covid-19 working group, National Technical Adv­isory Group on Immunisation (NT­AGI), told Business Standard that a mix of three things — immunity from natural infection, vaccine ind­uced immunity and the biology of the virus — is protecting the population. New variants are not causing serious illness. Arora says it’s important to monitor how many ca­ses are hospitalised with Covid and how many people are hospitalised due to Covid. As long as hospitalisations due to Covid are less, there is no reason for concern, he says. 

“But we need to continue surveillance and Insacog is doing that — sample surveillance, sewage surveillance and hospital surveillance. If there is a variant that can cause serious illness we need to pick it up fast — be pre-emptive and pro-active,” he adds. 
The Omicron wave peaked in January 2022 with over 300,000 cases. The daily new cases fell bel­ow 10,000 by March 2022. Another upsurge after this saw daily cases remain above the 10,000 mark between June and August 2022.

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The fourth time that the 10,000-mark was breached was in April 2023. The latest spike lasted 7 days — the shortest of the four.
Dr Umang Agrawal, infectious diseases consultant at PD Hinduja Hospital & Medical Research Centre in Mumbai, said that India has managed the recent spike in cases well. “The general immunity levels in the population acquired through natural infection and vaccination (hybrid immunity) has helped to tide over the spike in cases more efficiently,” he said.

But is herd immunity possible in Covid-19?
Agarwal feels that in case of influenza that has not been the case. People continue to get flu and also need to take an annual flu shot to protect against the ever evolving virus. There is something called ‘antigenic drift’, which involves accumulation of a series of minor genetic mutations, while an ‘antigenic shift’ involves ‘mixing’ of genes from flu viruses from different species. Agarwal feels that whenever an antigenic shift happens in the Sars-CoV-2 virus, then infections are likely to surge again.

He says we may need to get into a system of annual Covid-19 vaccinations just like influenza to keep the immunity boosted.
 The WHO ended the global emergency status for Covid-19 on May 5 after more than three years of declaring it in January 2020. Cou­ntries are now expected to manage the virus that has killed more than 6.9 million people worldwide along with other infectious diseases.

According to WHO, From a peak of more than 100,000 deaths per week in January 2021, Covid-19 deaths have slowed down to just over 3,500 a week in April 2023.
The virus is here to stay. In WHO’s words, “It is still killing and it is still changing. The risk remains of new variants emerging that cause new surges in cases and deaths.”

Is there a need for an annual Covid vaccine?
NK Arora, head, Covid-19 working group, National Technical Advisory Group on Immunisation (NTAGI) says that there is no clear answer to this question at the moment. 

The recent upsurge showed that those with precaution doses have fared similarly as those without. the coverage of influenza vaccine is very low, he says. 
“Even in countries where it’s available for free, the coverage levels are around 40 per cent,” he adds. 

Some vaccine makers are making options with Omicron strain. It’s important to have these options in our repertoire in case of any surge and need for vaccination.

First Published: May 14 2023 | 12:40 PM IST

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