New Delhi: In a study conducted on Saturday, the Indian Council of Medical Research (ICMR) reported that the combination of two different COVID-19 vaccines, Covaxin and Covishield, yielded better results than taking two doses of the same vaccine. The study included 98 people, 18 of whom were given Covishield as their first dose and Covaxin as their second, inadvertently.
According to the study, immunization with an adenovirus vector platform-based vaccine followed by an inactivated whole virus vaccine was not only safe, but also provided better immunogenicity.
The ICMR study also found that immunization with Covishield and Covaxin combined was safe and side effects were similar, compared to the same dose regimen. ‘To the best of our knowledge, this is the first study which reports the effects of heterologous prime-boost vaccination with an adenovirus vectored vaccine followed by an inactivated whole virus vaccine,’ the researchers said.
In India, COVID-19 vaccination started with two vaccines – adenovirus vector platform-based vaccine Covishield and inactivated whole virion BBV152 -Covaxin–and homologous prime-boost approach was followed. Under the national program, 18 individuals in Siddarthnagar, Uttar Pradesh inadvertently received Covishield as the first vaccination and Covaxin as the second.
When the nationwide vaccination program entered its fourth month, it was experiencing considerable anxiety in public awareness of vaccine hesitancy due to the mixed dosing. A study was conducted against this backdrop. In addition to these 18 individuals who received one dose of Covishield and a second dose of Covaxin, 40 individuals received two doses of Covishield and 40 individuals received two doses of Covaxin, were recruited in the study. The study lasted from May to June 2021.
‘We compared the safety and immunogenicity profile of them (18 individuals) against that of those receiving either Covishield or Covaxin. Lower and similar adverse events following immunization in all three groups underlined the safety of the combination vaccine-regime. Immunogenicity profile against Alpha, Beta and Delta variants in the heterologous group was superior and IgG antibody and neutralizing antibody response of the participants was also significantly higher compared to that in the homologous groups,’ the study stated. ‘The findings suggest that immunization with a combination of an adenovirus vector platform-based vaccine followed by an inactivated whole virus vaccine was not only safe but also elicited better immunogenicity,’ it said.
An analysis of reactogenicity was conducted using local and systemic AEFIs reported in the three groups within seven days after immunization. No one in the study who was vaccinated at the beginning or end of the study developed AEFI within 30 minutes of the first dose or second dose.
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Most commonly, local AEFI reported after the first and second dose is pain at the injection site. No other local AEFI such as erythema, induration, pruritis or pustule formation was reported by any of the participants. The most common clinical symptoms of systemic AEFI were pyrexia and malaise. No other systemic AEFIs such as urticaria, nausea, vomiting, arthralgia or cough were reported. In the study, the pyrexia was of low to moderate severity and was treated with paracetamol, subsiding in all participants within three to four days after vaccination.
‘Despite the high median age of the participants of the heterologous group (62 years) in our study, the reactogenicity profile demonstrated that mixing of the two vaccines based on different platforms is safe,’ the study said.
Study results show that a combination of an adenovirus vector platform-based vaccine and an inactivated whole virus vaccine is safe and elicits better immunity than two doses of homologous vaccination with the same vaccines. The findings have a major impact on the COVID-19 vaccination program, as heterologous immunisation will allow for better protection against variant strains of SARS-CoV-2.
The mixed regimens will also help reduce the challenge of vaccine shortages and remove hesitancy around vaccines, which could lead to programmatic ‘errors’ in setting where multiple COVID-19 vaccines are being administered, the study found. According to the study, however, a multicentre RCT is necessary to conclusively prove the findings.
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