Virendra Pandit
New Delhi: With more than two crore people already vaccinated in the country against the Covid-19 pandemic, a prestigious medical journal, citing the latest research, has said the Oxford University-AstraZeneca’s vaccine, known as Covishield in India, has a higher efficacy of 81.3 percent when the second dose is administered 12 weeks after the first.
That is, the second dose of this vaccine, being manufactured in the country by Pune-based Serum Institute of India (SII) under license from the developers, should be administered three months after the first for better results.
The immunogenicity studies conducted on participants younger than 55 years of age showed over a two-fold spike in IgG antibody response in those who had taken a dose at an interval of at least 12 weeks as compared to those who had an interval of fewer than six weeks.
During the study, published in The Lancet, researchers found Covishield’s efficacy to be only 55.1 percent when the two doses were administered less than six weeks apart. However, it was higher when the participants received one standard dose and another low dose as opposed to two standard doses, media reported on Tuesday.
The efficacy, according to the study, was 63·1 percent in those who received two standard doses and 80·7 percent in those who received the low dose, plus the standard dose, the study revealed.
The research was carried out by Ivan FN Hung from the Department of Medicine, University of Hong Kong, Queen Mary Hospital, Hong Kong, and Gregory A Poland from Mayo Vaccine Research Group, Mayo Clinic, Rochester, USA.
“Notably, in exploratory analyses, vaccine efficacy after a single standard dose was 76 percent from Day 22 to Day 90, and antibody levels were maintained during this period with minimal waning.
“Supporting a longer-interval immunization strategy, vaccine efficacy was significantly higher at 81·3 percent after two standard doses were given at an interval of 12 weeks or longer,” it said.
“Overall, the value of this study is in providing evidence that a single dose of the Covishield vaccine is highly efficacious in the 90 days after vaccination, a longer prime-boost interval results in higher vaccine efficacy, and that protection against symptomatic Covid-19 is maintained despite a longer dosing interval”.
However, with most of India’s more than 135 crore population yet to be vaccinated, amid variants of the pandemic re-surfacing globally, the four-month gap between the vaccine’s two doses is a major issue.
“For such a huge population, it will be difficult to vaccinate people after a three-month (12-week) gap from the first dose. People may not turn up due to many reasons for the second dose,” Dr. M.K. Sudarshan, Chairman, Karnataka’s Covid-19 Technical Advisory Committee, said.
Sources in the healthcare sector said the four-month-gap issue could be sorted out with the digital registration of beneficiaries. Sector regulator Indian Council of Medical Research (ICMR) will take this new study into consideration.