BENGALURU : While current government protocol states that the second dose of the vaccine must be administered 28 days after the first, new research on Covishield suggests that the booster dose might be more effective if the gap between the two doses is between 6-12 weeks.
India currently uses Bharat Biotech’s Covaxin, for which phase 3 trials are underway, and Oxford University’s Covishield. Experts have called on the government to consider the research on Covishield, which is being peer reviewed.
A recent study measuring the efficacy of a single dose and two-dose regimen of Covishield — developed by Oxford University and AstraZeneca - was posted on Preprints with The Lancet on February 1.
The study, which was done in the UK, found that with a single dose, vaccine efficacy was a sustained 76% from day 22 to day 90.
The efficacy rate rose to 82% when the second dose was taken 12 weeks after the first one. When the second dose was given less than six weeks after the first one, the efficacy rate was 54.9%.
Consultant physician Dr Manohar K N, who is due to get his second dose soon, said the central government must consider the new research and change the timing of the second dose to between 8-12 weeks.
“It would be preferable if health care providers are given a reasonable window to take the second dose. Many health care workers have apprehensions regarding vaccine efficacy and the gap between doses, which should be clarified so that we can set a trend for the public to follow. If doubts are left unaddressed, and vaccine acceptance is low among health workers themselves, the mammoth exercise undertaken by the central government could prove futile. Less people being vaccinated implies that there are lesser chances of developing herd immunity and preventing viral spread,” he said.
Senior epidemiologist and member of the state expert committee Dr Giridhara Babu said the government should consider giving the second dose of Covishield after 12 weeks.
“There is growing evidence which shows that when the second dose is given after 8-12 weeks, the vaccine has higher efficacy. But in terms of India, scientists have not tested beyond 28 days. From the beginning I have been saying, we should get the second dose after 12 weeks. For Covishield, it is advisable to give the second dose after 12 weeks.
However, there is no data on Covaxin. The vials we now have must be used to vaccinate all health care workers their first jab, and the second round of dosages must be used for the second dosage” he said.
An official from the health department however, said that there have been no changes in Central guidelines regarding the delaying of the second dose.