Tests to study the mixing of two different doses of COVID-19 vaccines is likely to begin in the next few weeks. The testing will be carried out using vaccines currently in use and those in the pipeline in a bid to boost efficacy and improve India's vaccination strategy.
The work on testing two different doses of vaccine is expected to begin in a few weeks, Dr NK Arora, chairman of the COVID-19 working group under the National Technical Advisory Group on Immunization (NTAGI), said as quoted by the Indian Express.
Arora said that approximately eight vaccines may be mixed and matched as part of the process. These will include the three vaccines approved for use in India at present -- Serum Institute of India's Covishield, Bharat Biotech's Covaxin, and the Russian vaccine Sputnik V.
Clinical testing may be carried out in collaboration with the Indian Council of Medical Research (ICMR) and companies that develop and produce these vaccines, the report said.
Frequently Asked Questions
A vaccine works by mimicking a natural infection. A vaccine not only induces immune response to protect people from any future COVID-19 infection, but also helps quickly build herd immunity to put an end to the pandemic. Herd immunity occurs when a sufficient percentage of a population becomes immune to a disease, making the spread of disease from person to person unlikely. The good news is that SARS-CoV-2 virus has been fairly stable, which increases the viability of a vaccine.
There are broadly four types of vaccine — one, a vaccine based on the whole virus (this could be either inactivated, or an attenuated [weakened] virus vaccine); two, a non-replicating viral vector vaccine that uses a benign virus as vector that carries the antigen of SARS-CoV; three, nucleic-acid vaccines that have genetic material like DNA and RNA of antigens like spike protein given to a person, helping human cells decode genetic material and produce the vaccine; and four, protein subunit vaccine wherein the recombinant proteins of SARS-COV-2 along with an adjuvant (booster) is given as a vaccine.
Vaccine development is a long, complex process. Unlike drugs that are given to people with a diseased, vaccines are given to healthy people and also vulnerable sections such as children, pregnant women and the elderly. So rigorous tests are compulsory. History says that the fastest time it took to develop a vaccine is five years, but it usually takes double or sometimes triple that time.
"We are looking for a combination of vaccines that provide better protection. At the moment, the vaccines used are providing protection against severe disease, but they are not providing protection from infection and transmission of the virus to the extent that we would have liked," Dr Arora said, as per the report.
He also said that while vaccines are safe individually, the focus is to see "if they are safe together."
"These vaccines are produced in different platforms and we do not want them to create difficulty and create complications, so every vaccine will probably not be possible to mix and match," he added, as per the report.
Notably, after 20 people in Uttar Pradesh mistakenly received both Covishield and Covaxin doses, the centre had said that "two different doses are safe".
NITI Aayog member (Health) Dr VK Paul had said the government is planning to mix and match (vaccine doses) on a trial basis.
A recent study (not peer reviewed) in Spain found people had a vastly higher antibody response 14 days after receiving the Pfizer booster, following an initial dose of AstraZeneca.
The study found most side effects were mild or moderate and short-lived (two to three days), and were similar to the side effects from getting two doses of the same vaccine.
Besides, in a UK mix and match study published in The Lancet in May, 830 adults over 50 were randomised to get either the Pfizer or AstraZeneca vaccines first, then the other vaccine later.Click here for Moneycontrol's full coverage of COVID-19