BENGALURU: An international study has established that the Oxford University- AstraZeneca’s Covid vaccine known as Covishield in India has a higher efficacy of 81.3 per cent when the second dose was given 12 weeks after the first.
Moreover, immunogenicity studies conducted on participants younger than 55 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 less than six weeks.
During the study, published in The Lancet, researchers found Covishield’s efficacy to be only 55.1 per cent when the two doses were administered less than six weeks apart but was higher when the participants received one standard dose and another low dose as opposed to two standard doses.
The efficacy was 63·1 per cent in those who received two standard doses and 80·7 per cent in those who received the low dose plus the standard dose, as per the study conducted by Ivan FN Hung from Department of Medicine, University of Hong Kong and Queen Mary Hospital, Hong Kong, and Gregory A Poland from Mayo Vaccine Research Group, Mayo Clinic, Rochester, US.
“Notably, in exploratory analyses, vaccine efficacy after a single standard dose was 76 per cent from Day 22 to Day 90 , and antibody levels were maintained during this period with minimal waning.
Supporting a longer-interval immunisation strategy, vaccine efficacy was significantly higher at 81·3 percent after two standard doses were given at an interval of 12 weeks or longer,” the study states.
“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,” the study states.
However, Dr MK Sudarshan, Chairman, Karnataka’s Covid-19 Technical Advisory Committee, said they decided on a four-week gap between two doses after the expert group debated on similar studies done earlier.
“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,” he said.
However, a doctor from the Federation of Healthcare Associations of Karnataka, said, “It is possible if issues with the Co-WIN portal are fixed. Indian Council of Medical Research will take this new study into consideration.”