Explained | Pig-to-human heart, India’s appeal against WTO sugar verdict, TRP resumption, and vaccination effect on Omicron

Explained | Is vaccination limiting Omicron’s virulence?

WHO has asked manufacturers to provide data on the performance of COVID-19 vaccines.

WHO has asked manufacturers to provide data on the performance of COVID-19 vaccines.

The story so far : Omicron, the latest SARS-CoV-2 variant of concern, may be pushing up COVID numbers across the world but it is also reporting a lower rate of hospitalisation and deaths compared to the previous Delta waves so far. This, despite the fact, that mutations on Omicron spikes are associated with higher transmissibility and immune evasion. Since its emergence, the SARS-CoV-2 virus has continued to evolve and the World Health Organization (WHO) has designated five of them as variants of concern — Alpha, Beta, Gamma, Delta and Omicron — due to their impact on transmission, disease severity, or capacity for immune escape. While the Omicron variant is spreading rapidly across the world, the evolution of SARS-CoV-2 is expected to continue and Omicron is unlikely to be the last variant of concern.

What is the impact of the current vaccines on Omicron?

According to WHO, the threat posed by Omicron largely depends on four key questions -- how transmissible the variant is, how well vaccines and prior infection protect against infection, transmission, clinical disease and death, how virulent the variant is compared to other variants and how populations understand these dynamics, perceive risk and follow control measures, including public health and social measures.


“Vaccines are not disease-modifying but they have a positive impact in controlling severity of the disease, reducing the rate of hospitalisation and possible adverse outcome,’’ said Balram Bhargava, director general, Indian Council of Medical Research, at the Health Ministry’s weekly press conference. This comes close on the heels of experts also cautioning against trivialising the impact of Omicron. “Deaths are a delayed estimate; the impact of COVID-19 impacting care is not usually quantified,” tweeted Vinod Scaria, scientist at CSIR Institute of Genomics and Integrative Biology.

With available COVID-19 vaccines, the current focus remains on reducing severe disease and death, as well as protecting health systems.

The WHO states that for the Omicron variant, the mutational profile and preliminary data indicate that vaccine effectiveness will be reduced against symptomatic disease caused by it, but protection against severe disease is more likely to be preserved. “However, more data on vaccine effectiveness, particularly against hospitalisation, severe disease, and death are needed, including for each vaccine platform and for various vaccine dosing and product regimens,” it added. Earlier in the week, as cases surged across India, vaccine manufacturer Bharat Biotech announced that its booster dose has now shown to neutralise both Omicron and the Delta variant of SARS-CoV-2. “100 % of the test serum samples showed neutralisation of the Delta variant and more than 90% of serum samples showed neutralisation of the Omicron variant,” it said in a statement.


Why do vaccine manufacturers need to provide data?

Experts across the globe agree that COVID-19 vaccines impact the spread of infection and transmission, in addition to the prevention of severe disease and death. In the interim, WHO has encouraged COVID-19 vaccine manufacturers to generate and provide data on performance of current and Omicron-specific COVID-19 vaccines. “COVID-19 vaccines need to be based on strains that are genetically and antigenically close to the circulating SARS-CoV-2 variant(s) and in addition to protection against severe disease and death, be more effective in protection,’’ noted WHO. “The challenge of continuing to ensure the production of the best possible vaccines in a timely manner requires a continuous exchange of information and collaboration,” it said.


Is the hospitalisation rate during the Omicron led-wave low so far?

Studies from South Africa and the U.K. indicate that people infected with Omicron were 50-70% less likely to be admitted to hospital than those infected with Delta. According to V.K. Paul, NITI Aayog member (health), in India the hospitalisation rate due to Omicron is at 5-10%, compared to 20% during the Delta wave. But a health official cautioned that it is still early days and Omicron cannot be labelled mild, moderate or severe as yet. “We may have less hospitalisation now but the virus is spreading fast and we need to be careful. We are currently seeing less severity of symptoms in the vaccinated so it is extremely important to get the vaccine,” he said. Over the last 24 hours, over 2 lakh new cases of COVID-19 have been reported. According to the Health Ministry, in all, 6,041 Omicron cases have been detected so far.

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Printable version | May 21, 2022 11:39:25 am | https://www.thehindu.com/news/national/explained-is-vaccination-limiting-omicrons-virulence/article38275807.ece