Taking two different Covid vaccines?

Vaccinating people with both the Oxford–AstraZeneca and Pfizer–BioNTech COVID-19 vaccines produces a potent immune response against the virus SARS-CoV-2, researchers conducting a study in Spain have found. Preliminary results from the trial of more than 600 people — announced in an online presentation on 18 May — are the first to show the benefits of combining different coronavirus vaccines. A UK trial of a similar strategy reported safety data last week, and is expected to deliver further findings on immune responses soon.

Researchers hope that such mix-and-match COVID-19 vaccination regimens will trigger stronger, more robust immune responses than will two doses of a single vaccine, while simplifying immunization efforts for countries facing fluctuating supplies of the various vaccines. This strategy of mixing different vaccines is known as a heterologous prime and boost, which has been deployed for vaccines against other diseases, such as Ebola.

But such strategies have to be deployed by the Government. As an individual, we don't get to pick. But recently some study in India has shown that a combination of two vaccines like Covishield and Covaxin one after the other offers a better immunity system. It's always better to get 2 shots of the same vaccine. Manufacturer recommends so. However if you fail to do so, or accidentally take another vaccine as 2nd dose, there is no need to panic. Just inform your nearby health facility regarding that. No recommendation for additional doses so far.

A combination of Covishield and Covaxin vaccines elicits better immunogenicity than two doses of the same vaccine, the Indian Council of Medical Research (ICMR) said on Sunday 8th August 2021. The Council released its findings which suggest that immunisation 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.

The immunisation programme against COVID-19 in India started with two vaccines — AstraZeneca’s ChAdOx1-nCov-19 (named Covishield in India) and inactivated whole virion BBV152 (Covaxin). A homologous prime-boost approach was followed. However, 18 individuals, under the national program, inadvertently received Covishield as the first jab and Covaxin as the second. In its study, the ICMR has compared the safety and immunogenicity profile of these persons against that of individuals receiving either Covishield or Covaxin.

The pre-print report titled “Serendipitous COVID-19 Vaccine-Mix in Uttar Pradesh, India: Safety and Immunogenicity Assessment of a Heterologous Regime,” has not been certified by peer review and should not be used to guide clinical practice, the Council said. It, however, maintained that the findings have an important implication for the COVID-19 vaccination program wherein heterologous immunisation will pave the way for induction of improved and better protection against the variant strains of SARS-CoV-2.

“Such mixed regimens will also help to overcome the challenges of shortfall of particular vaccines and remove hesitancy around vaccines in people’s mind that could have genesis in programmatic ‘errors’ especially in settings where multiple COVID-19 vaccines are being used. However, to conclusively prove these findings a multi-centre RCT needs to be carried out,” the ICMR said. WHO cautions. Previously the World Health Organisation had warned against mixing of vaccines, saying there was very little information on the mix-and-match of vaccines. It advised against people mixing and matching vaccines from different manufacturers, calling it a “dangerous trend” since there was little data available about the health impact.

The Council admitted that there are few limitations to their study. “The sample size was small and the participants were put under a short follow up period of only 60-70 days after immunisation with the first dose and baseline serological and immunological data of the participants not available,” it said. It, however, added that there are several major strengths in the study. “This is the first report of heterologous immunisation with an adenovirus vector based and an inactivated whole virion vaccine in humans demonstrating safety and significantly improved immunogenicity,” it noted. Additionally comparable proportion of solicited adverse event following immunization in the

A study by ICMR involving 98 people, 18 of whom had inadvertently received Covishield as first dose and Covaxin as the second in Uttar Pradesh, showed that combining these two Covid-19 vaccines elicited better immunogenicity than two doses of the same vaccine. The study also found that immunisation with combination of Covishield and Covaxin was safe and the adverse effects were also found to be similar when compared to the same dose regimen. The study titled Serendipitous COVID-19 Vaccine-Mix in Uttar Pradesh, India: Safety and Immunogenicity Assessment of a Heterologous Regime' has been uploaded on medRxiv, a preprint server and is yet to be peer reviewed.

"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. The immunisation program against COVID-19 in India started with two vaccines--adenovirus vector platform-based vaccine Covishield and inactivated whole virion BBV152 -Covaxin--and homologous prime-boost approach was followed. However, 18 individuals, under the national program, in Siddarthnagar, Uttar Pradesh inadvertently received Covishield as the first jab and Covaxin as the second.

The nationwide vaccination program at this time had entered in its fourth month of its existence and the event of mixed dosing raised considerable anxiety in public domain with a potential to contributing to vaccine hesitancy. The study was conducted against this backdrop. So, including these 18 individuals who had received one dose of Covishield and second dose of Covaxin, 40 recipients of two doses of Covishield and 40 recipients of two doses of Covaxin, were recruited in the study. The study duration was 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 immunisation 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 neutralising antibody response of the participants was also significantly higher compared to that in the homologous groups," the study stated.

"The findings suggest that immunisation 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. The reactogenicity analysis was carried out based on solicited local and systemic AEFIs reported in the three groups within seven days of immunisation. None of the participants enrolled in the study had any serious AEFI within 30 minutes of immunisation with the first or second dose.

The most common local AEFI reported after first and second dose was pain at injection site. No other local AEFI such as erythema, induration, pruritis or pustule formation was recorded by any of the participants. Most commonly reported systemic AEFI were pyrexia and malaise. No other systemic AEFIs like urticaria, nausea, vomiting, arthralgia or cough was reported. The pyrexia was of low to moderate grade and was managed by administration of paracetamol and subsided in all participants within three to four days post vaccination, according to the study. "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.

The study demonstrates that immunisation with a heterologous combination of an adenovirus vector platform-based vaccine followed by an inactivated whole virus vaccine is safe and elicits better immunogenicity than two doses of homologous vaccination, using the same vaccines. These findings have an important implication for the COVID-19 vaccination program wherein heterologous immunisation will pave the way for induction of improved and better protection against the variant strains of SARS-CoV-2. Such mixed regimens will also help to overcome the challenges of shortfall of particular vaccines and remove hesitancy around vaccines in people's mind that could have genesis in programmatic 'errors' especially in settings where multiple COVID-19 vaccines are being used, the study highlighted. However, to conclusively prove these findings a multi-centre RCT needs to be carried out, the study underlined. Cheers!