Dr Reddy's Laboratories has sought permission from India's drug regulator to conduct a phase-3 clinical trial to evaluate the efficacy and safety of the Sputnik Light vaccine as a booster dose against COVID-19 in India, sources said on 9 December.

For our comprehensive coverage and latest updates on COVID-19 click here.

Stating the Sputnik Light is the Component 1 of the Gam-COVID-Vac Combined Vector Vaccine (Sputnik V), P Madhavi, the Director-Regulatory Affairs at Dr Reddy's Laboratories, proposed to use batches of the vaccine manufactured at Hetero Biopharma Limited, Telangana, and at its loan license facility at Shilpa Biologicals Private Limited in Karnataka for the phase-3 trial.

Sputnik Light has not yet received emergency use authorisation from the Drugs Controller General of India (DCGI). "Seeking your permission to conduct 'a phase-3 randomised, open-label three-arm, multi-centre, clinical study in parallel assignment to evaluate immunogenicity and safety of a booster dose of Sputnik Light vector vaccine against COVID-19 in healthy Indian subjects," a source quoted Madhavi as having said in the application.

Recently, the Serum Institute of India sought from DCGI approval for Covishield as a booster dose citing adequate stock of the vaccine in the country and a demand for a booster shot due to the emergence of new coronavirus variants. In an application to the DCGI, Prakash Kumar Singh, the Director, Government and Regulatory Affairs at Serum Institute cited that the UK's Medicines and Healthcare products Regulatory Agency has already approved the booster dose of AstraZeneca ChAdOx1 nCoV-19 vaccine.

The INSACOG, in its bulletin dated November 29, recommended a booster dose of COVID-19 vaccines for those above 40 years with preference to high-risk and high-exposure populations. However, later it said their recommendation was not for the national immunisation programme as many more scientific experiments are required to assess its impact. Justifying the need for a booster dose six months after the second dose for all adult population instead of the high-risk population, Madhavi in the application said, "After getting vaccinated against COVID-19, protection against the virus may decrease over time and be less effective against the Delta variant."

"Declining VNA titers may herald significant declines in effectiveness against severe disease. The recent emergence of highly transmissible variants of SARS-CoV-2 has led to considerations for booster doses to enhance immunity and provide sustained protection from COVID-19.

"Emerging evidence shows that among healthcare and other frontline workers, vaccine effectiveness against COVID-19 decreases rapidly due to the combination of waning immunity and the greater exposure to virus including variants," the source quoted Madhavi as having stated in the application.

A booster dose of COVID-19 vaccines administered months after primary vaccination is expected to augment immunity against the virus, including neutralising capacity against the variants of concern, she said.

The benefits of booster dose are expected to be seen in the entire adult population and not just elderly or high-risk cases. Both Pfizer and Moderna had conducted their booster dose studies in the overall adult population demonstrating an increase in immunogenicity titres post-administration of the booster dose, Madhavi said.

"We intend to assess the safety and immunogenicity of a booster dose of Sputnik Light vector vaccine when administered at least six months after primary vaccination with Covaxin or Covishield," she said in the application.

The union health minister had recently informed the Lok Sabha that the National Technical Advisory Group on Immunisation and the National Expert Group on Vaccine Administration for COVID-19 are deliberating and considering scientific evidence for administering booster doses.