Omicron BF.7: Is mixing Covid vaccines more effective against the new subvariant? What experts say

Amid rising cases of Omicron BF.7 in China and other parts of the world, there has been concerns of a fresh wave triggered by the subvariant in India in the coming months. Omicron BF.7 was first found in India in July and so far, just 4 cases have been detected across Gujarat and Odisha. Experts say we do not need to press the panic button as yet but at the same time renew social distancing measures and keep our guards on. (Also read: Omicron BF.7: Cases of highly infectious strain rise in India; experts on symptoms, precautions and fresh wave)

Getting booster shots is one of the ways to boost immunity against the new variant. According to a new AIG study, Hyderabad-based Biological E's Corbevax booster in individuals already vaccinated with Covishield can offer maximum protection against Omicron variants. The study found that people who were given Corbevax showed higher levels of antibodies.

Following incidents of people inadvertently taking different vaccines in two separate doses, Indian Council of Medical Research (ICMR) study found that mix and match of vaccines had no adverse effect. There has, however, been concern around whether it is safe or mixing of two different vaccines could actually be more effective and provide better shield against different variants of Coronavirus.

So, can combining vaccines offer better protection against Omicron BF.7 and new emerging subvariants? We asked experts.

'MIXING SHOTS A PROMISING STRATEGY'

"Mixing Covid shots or what we call as heterologous boosting is a promising strategy in our fight against this pandemic. As per limited research it has been found that waning immunity is a concern in giving us protection from the virus. Mixing shots such as vector-based vaccines (Covishield) followed by mRNA based (Pfizer) can result in boosted or better immune protection. mRNA based vaccines generate a good antibody response and vector-based vaccines provide a good T Cell response. So, a combination of both seems to provide a promising protection," says Dr. Shivanshu Raj Goyal, Consultant Pulmonologist, Artemis Hospitals, Gurugram.

"Side effects can vary from individuals but mixing vaccines is a good strategy to provide safe and effective protection and in some cases mixing vaccines mount lifetime immunity by kicking memory B and T cells into action, less seen otherwise. Whatever strategy we should follow and most beneficial to all would be updated timely by MoHFW on timely intervals and should be followed," says Dr Goyal.

'NO SIDE EFFECTS, IT CAN BOOST IMMUNITY'

"Mass Covid vaccination has played a key role in limiting the severity of Covid waves across India. Various Covid vaccines have been used globally after scientific approval the curb this pandemic. With the recent news of new variants, booster dose is to protect you and enhance your protection against severe covid infections. Sometimes availability or shortage of the same make of vaccine is a problem. However, mixing the vaccines has no side effects rather it can boost the immunity and give multiple ways to our immune system to identify the offending virus and act rapidly," says Dr Rahul Sharma, Additional Director Pulmonology, Fortis Hospital Noida.

'Mixing Covid vaccines need of the hour'

Covid vaccines booster strategy is need of the hour. Usually, sequential boosters are recommended.

Mixing heterologous immune response is an emerging concept. In initial US-based trials and studies it was observed that though it was necessity borne intervention turned out to be useful owing to mixing of vaccines resulted in increase in type of immune responses and potential prolonged immunogenic effect. Researchers have found that following one dose of the AstraZeneca with a dose of the Pfizer-BioNTech vaccine produces more stronger and better immune responses, as measured by blood tests.

Mixing vaccines gives advantage in pathogen recognition and better immunogenic responses in terms of all arms of immunity, says Dr Neha Rastogi Panda, Consultant Infectious Diseases, Fortis Memorial Research Institute, Gurugram.

'Mixing of vaccines proven to be non-inferior or superior'

"Government of India has permitted the usage of Corbevax vaccine as a precaution dose after completion of six months from administration of second dose of either Covaxin or Covishield vaccines in adult population in August 2022. Decision of this by Covid-19 working Group was based on scientific evidence generated through double blinded randomised control trial of Corbevax vaccine phase-3 clinical study evaluating immunogenicity and safety of booster dose Corbevax vaccine in adult volunteers previously vaccinated with two doses of either Covaxin or Covishield. As per the global scientific evidence, usage of mixing of two different vaccines have been proven to be non-inferior or superior as compared to single vaccine usage in Covid-19 illness in terms of immunogenicity which is measured by antibodies level and T cell mediated immunity measured by CD4 and CD8 levels," says Dr Manoj Sharma, Senior Consultant, Internal medicine, Fortis Hospital Vasant Kunj.

"Mixing of two different vaccines may give the immune system multiple ways to recognise a pathogen (Virus). In a Spanish study, 448 individuals who received a mix of AstraZenecia dose followed By Pfizer BioNTech dose, robust immune response was noted with fewer side effects. Similarly, Sputnik vaccine when combined with AstraZenecia also revealed stronger immune response," says Dr Sharma.

Benefits of heterologous vaccination

Although the approved COVID vaccines provide a high level of protection against symptomatic infection and severe illness, there is increasing evidence to suggest waning of immunity over time. Also, it has been seen that some of the subvariants/sub lineages are immune-evasive i.e., can cause infection in those already having some immunity against SARS CoV-2 virus. Heterologous vaccination approach refers to the mixing of more than one type of vaccines. There are reasons to believe that immunization with different types of vaccines might provide immunological advantages. Mixing of vaccines provides a broadened level of protection, and for a longer duration. There is sufficient scientific data available to date to suggest superior immunological response with heterologous vaccines approach. Studies have shown better and prolonged immunological response following mixing and matching, both inactivated as well as mRNA-based vaccines. This benefit has been found with mixing of vaccines in primary series as well as booster dosing," says Dr Rohit Kumar Garg, Consultant, Department of Infectious Diseases, Amrita Hospital, Faridabad.

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