NEW DELHI: Neutralising antibody levels waned after six months in those who were fully vaccinated against the coronavirus with Covishield, Covaxin and a mix of both - Covishield as the first dose and Covaxin as the second dose - with regard to Omicron variant, a study done by the National Institute of Virology (NIV) in Pune has indicated.

The heterologous vaccination regimen of administering the first dose of Covishield, followed by the second dose of Covaxin, however, had given a very good neutralising response against Delta and other Variants of Concern, Dr Pragya Yadav, a scientist at the NIV, said.

The study findings were published in the Journal of Travel Medicine recently.

The study involved three cohorts -- a heterologous group with 18 individuals who were inadvertently administered the first dose of Covishield and the second dose of Covaxin in Uttar Pradesh and the other two groups comprising 40 individuals each receiving two doses of homologous Covishield or Covaxin.

"All the three groups were closely monitored. When we analysed the cohorts in June last year, the heterologous vaccination regimen of administering the first dose of Covisheid, followed by the second dose of Covaxin showed a very good neutralising antibody response against Delta and other Variants of Concern, as compared to the two other cohorts," Yadav said.

We analysed them again in December last year. A significant reduction in neutralizing antibody levels was observed in all cohorts with regard to Omicron, she said.

The study findings have so far highlight the need for booster dose in the context of Omicron variant, she added.

"The gradual shift of VoCs from Delta to Delta-sub-lineage to Omicron, along with the observed waning of immunity post six months of vaccination, has prompted discourses around devising an innovative vaccination strategy. The present investigation findings contribute meaningfully to such discussions. Regardless of the findings of this study, longitudinal monitoring for breakthrough infections should remain a part of any surveillance system," the study stated.

India began administering the precaution doses of the COVID-19 vaccines to the healthcare and frontline workers and those aged 60 years and above with comorbidities from January 10.

The Union health ministry removed the comorbidity clause recently, making everyone aged above 60 years eligible for the precaution dose of the Covid vaccines.

The vaccination of children aged 12-14 years started from March 16.

Beyond Delta: Scientist Track Other Coronavirus Variants With Potential Threat

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Concerning Mutation

The continued spread of the SARS-CoV-2 virus has spawned a Greek alphabet of variants - a naming system used by the World Health Organization (WHO) to track concerning new mutations of the virus that causes COVID-19. Some have equipped the virus with better ways of infecting humans or evading vaccine protection.

Scientists remain focused on Delta, now the dominant variant around the world, but are tracking others to see what may one day take its place.

Delta - Still Dominant

The Delta variant first detected in India remains the most worrisome. It is striking unvaccinated populations in many countries and has proven capable of infecting a higher proportion of vaccinated people than its predecessors.

The WHO classifies Delta as a variant of concern, meaning it has been shown capable of increasing transmissibility, causing more severe disease or reducing the benefit of vaccines and treatments.

According to Shane Crotty, a virologist at the La Jolla Institute for Immunology in San Diego, Delta's "superpower" is its transmissibility. Chinese researchers found that people infected with Delta carry 1,260 times more virus in their noses compared with the original version of the coronavirus. Some U.S. research suggests that the viral load in vaccinated individuals who become infected with Delta is on par with those who are unvaccinated, but more research is needed.

While the original coronavirus took up to seven days to cause symptoms, Delta can cause symptoms two to three days faster, giving the immune system less time to respond and mount a defense.

Lambda – On The Wane

The Lambda variant had attracted attention as a potential new threat, but this version of the coronavirus, first identified in Peru in December, appears to be receding.

Although cases involving Lambda were rising in July, reports of this variant have been falling globally for the past four weeks, according to data by GISAID, a database that tracks SARS-CoV-2 variants.

The WHO classifies Lambda as a variant of interest, meaning it carries mutations suspected of causing a change in transmissibility or causing more severe disease, but it is still under investigation. Lab studies show it has mutations that resist vaccine-induced antibodies.

Mu - One To Watch

Mu, the variant formerly known as B.1.621, was first identified in Colombia in January. On Aug. 30, the WHO designated it as a variant of interest due to several concerning mutations, and assigned a Greek letter name to it.

Mu carries key mutations, including E484K, N501Y and D614G, that have been linked with increased transmissibility and reduced immune protection.

According to the WHO's Bulletin published last week, Mu has caused some larger outbreaks in South America and Europe. While the number of genetic sequences identified as Mu have fallen below 0.1% globally, Mu represents 39% of variants sequenced in Colombia and 13% in Ecuador, places where its prevalence has "consistently increased," WHO reported.

The global health agency said it continues to monitor Mu for changes in South America, especially in areas where it is co-circulating with the Delta variant. Maria van Kerkhove, head of WHO's emerging diseases unit, said circulation of the variant is decreasing globally but needs to be observed closely. In a press briefing last week, White House chief medical advisor Dr. Anthony Fauci said U.S. officials are watching it, but so far Mu is not considered an immediate threat.

More On The Way?

Getting more people vaccinated against COVID-19 is critical as large groups of unvaccinated people give the virus more opportunity to spread and mutate into new variants.

That effort must be stepped up internationally to keep variants from emerging unchecked among the populations of poor nations where very few people have been inoculated, experts say.

Even so, while the current vaccines prevent severe disease and death, they do not block infection. The virus is still capable of replicating in the nose, even among vaccinated people, who can then transmit the disease through tiny, aerosolized droplets.

To defeat SARS-CoV-2 will likely require a new generation of vaccines that also block transmission, according to Dr. Gregory Poland, a vaccine developer at the Mayo Clinic. Until then, Poland and other experts say, the world remains vulnerable to the rise of new coronavirus variants.

Still didn't get your booster shot? Study says it is necessary to fight against Omicron

Neutralising antibody levels wane after 6 months in those who were fully vaccinated for Covid.

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Beyond Delta: Scientist Track Other Coronavirus Variants With Potential Threat

Concerning Mutation

Delta - Still Dominant

Lambda – On The Wane

Mu - One To Watch

More On The Way?

Read More News on

Still didn't get your booster shot? Study says it is necessary to fight against Omicron

Neutralising antibody levels wane after 6 months in those who were fully vaccinated for Covid.

Related

Beyond Delta: Scientist Track Other Coronavirus Variants With Potential Threat

Concerning Mutation

​Delta - Still Dominant

​Lambda – On The Wane

​Mu - One To Watch

​More On The Way?

Read More News on

Delta - Still Dominant

Lambda – On The Wane

Mu - One To Watch

More On The Way?