Increasing gap in two doses of Covishield, necessary or helpless for science?
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Dr. Swapnil Parikh says, “This decision is clearly related to supply. However, this is the right decision. ”
The Covishield being used in India against Novel Coronavirus was approved in early January 2021 under Emergency Use. It was approved with a gap of 28 days between doses. At that time, the UK had already recommended an interval of 4–12 weeks, the first country to approve this vaccine for Oxford AstraZeneca.
On 22 March, the government again changed the advisory and said that the dose gap should be increased by 6-8 weeks. At that time, a study in the medical journal The Lancet , including several studies, established that a 12-week interval led to better efficacy.
The government has decided to increase the time between getting 2 doses of Covishield vaccine from 6-8 weeks to 12-16 weeks. This is the second time in 3 months that the time between doses of the covishield vaccine has been extended.
On 13 May, the Ministry of Health accepted the recommendation of the National Expert Group on Vaccine Administration (NEGVAC) based on ‘UK evidence’ regarding vaccine efficacy under the chairmanship of Dr VK Paul .
An important question arises when India changes its decisions about the gap between repeated doses of Covishield – is it a science-based decision or supply shortage has forced the government to adopt ‘better’ public health measures.
Dr. Swapnil Parikh, an internal medicine doctor and scientist, says, “This decision is clearly related to supply. That is why it is said that this is the right decision.”
What does science say?
The recommendation was made by the COVID Working Group headed by Dr. NK Vohra. Other members include Dr. Gagandeep Kang, Dr. JP Mulial and Dr. VG Somani of Drugs Controller General of India (DCGI).
12-week interval
In February 2021, The Lancet published a study based on data from 4 different trials and found that Covishield’s efficacy was close to 55.1% when the dose interval was less than 6 weeks. After an interval of 12 weeks, the efficacy increased to 81.3%.
Also in February, an article in the British Medical Journal (BMJ) stated that a single dose of vaccine in the first 90 days after vaccination gave a total of 76% protection against Symptomatic Covid-19. But this was not his time limit.
The UK Regulators and the European Medicine Agency (EMA) recommend a 12-week interval for the AstraZeneca vaccine. The World Health Organization (WHO) recommends an interval of 8–12 weeks between doses.
16-week interval
Some countries, such as Spain and Canada, have increased the interval to 16 weeks for certain age groups. But no trials have been conducted to support the 16-week gap.
According to a Reuters report, Spain’s decision was motivated by the need to evaluate the results of trials on a mixture of different vaccines, before deciding whether those age-group groups were given a second AstraZeneca shot or any other drug. will be given. After this, blood clots were reported in some parts of Europe with the AstraZeneca vaccine.
“For a long time, a 3-month interval would be better than a 1-month interval” – Dr. Gangandeep Kang
In an earlier interview with Fit , CMC Vellore microbiologist Dr Gagandeep Kang supported a 12-week gap. Dr. Kang is part of the group on whose recommendation the government has decided to widen the gap for Covishield.
Dr. Kang said that this will not only help in dealing with the lack of vaccine, but will also provide better efficacy in the long run.
“The UK decided early on that for both Pfizer and the Covishield vaccine, they would keep the difference between the other doses up to 3 months. Now we have data on what single dose of AstraZeneca vaccine can achieve. Single dose provides better protection against hospitalization and death. It can provide protection for at least 3 months. If there is a problem with the supply, you can safely delay up to 3 months with the AstraZeneca vaccine. ”
She continues- “A 3-month interval is better than a 1-month interval.” Immunologically, in the long run, increasing the gap between the 2 doses will give you more protection and we do not want to rush around to take booster doses. ”
Speaking to Fit, Dr. Swapnil Parikh said,
“It should never have happened this way, we should have a better plan, but if it didn’t, then we would have to work with what we have. In the crisis we are in now, we have to This seems the least terrible option. This is to save more lives. ”
What about covaxin? Can we delay the second dose?
For now, the panel has not recommended any change in the 28-day dosing schedule for covaxin. Vaccine manufacturer Bharat Biotech has not yet released complete data for the Phase 3 trial of Covaxin, nor is there any data publicly available on the efficacy of Covaxin’s single dose, nor is there any real-world data that has investigated it Should be
But Dr. Parikh points to an interesting model that assesses the public health impact of delaying the second dose.
This model, featured in BMJ, is about Pfizer’s mRNA vaccine, with standard vaccination prioritizing the first dose and delaying the second dose.
Results indicated that delaying the second dose may reduce cumulative mortality in some special circumstances, at least for people under 65 years of age.
While this was a simulation of the Pfizer vaccine itself, Dr. Parikh says, “If the single dose efficacy of covaxin is more than 70%, then we can consider a strategy for covaxin where we ensure that 65 People older than age can get their second dose according to the schedule of 28 days, while for the people of 45-65 years, the second dose can be delayed up to 90 days. ”
6 months wait for vaccine after infection
A second recommendation by the National Immunization Technical Advisory Group is yet to be adopted, that is, a 6-month wait for the vaccine after COVID infection.
On May 1, guidelines were issued by the Health Ministry on when you can take your second dose after the infection. It was recommended for 2–8 weeks after the symptoms subsided.
So what exactly should be the difference?
WHO does not specify a difference.
The US CDC also does not specify the difference – if you naturally recover automatically. However, it recommends that if you are treated with monoclonal antibodies or plasma, you should wait 90 days before taking the vaccine.
There is not enough data to say how long a natural immunity will persist from infection, but there are data that suggest that even if antibodies have disappeared, T cell immunity will protect you.
Parikh says, “We know that even if you become infected again, it is unlikely to be serious.” Right now we are not thinking about what is best for a person, but rather what is best collectively. ”
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