Because of their inexpensive cost, vaccinations made with inactivated SARS-CoV-2 viruses are widely used in underdeveloped countries. As per new research from Sweden’s Karolinska Institutet, a booster shot of mRNA vaccine given after two doses of inactivated vaccination provides the same layer of safety versus COVID-19 as 3 doses of mRNA vaccine. The findings have been published in Nature Communications, one of the journals.
The findings suggest that one booster shot of an mRNA vaccine, in addition to the less expensive but less effective inactivated vaccines, is adequate to attain the ‘gold-standard’ immune reaction calculated after three doses of an mRNA vaccine, says Karolinska Institutet’s Department of Biosciences and Nutrition’s professor Qiang Pan Hammarström. Even in resource-poor countries, which would probably be a great investment to defend against severe COVID-19.
A total of 175 healthy volunteers with varied vaccination histories participated in the study. After immunisation and booster doses with an immobilised vaccine (Sinovac/Sinopharm), mRNA vaccine (Pfizer-BioNTech/Moderna), or a blend of both, the researchers looked for antibody and memory B and T cell responses against SARS-CoV-2.
The findings revealed that giving an mRNA vaccine booster shot to people who had already gotten two doses of inactivated vaccine significantly increased the levels of nullifying antibodies and memory B and T cells targeted towards SARS-CoV-2 variants of concern, particularly Omicron. The levels were much greater than those seen in people who received three doses of inactivated vaccination and were comparable to that seen in those who received three doses of mRNA vaccine or a booster of mRNA vaccine after a natural illness.
Since nearly half of the COVID-19 vaccine doses supplied worldwide are inactivated shots, an enhanced mRNA booster technique could help billions of people in their fight against developing variations of worry, explains Qiang Pan Hammarström. A wider usage of mRNA booster doses could also help China overcome its current restrictions. The small number of participants in the trial is a restriction; just 16 people were vaccinated with 2 doses of inactivated vaccine accompanied by an mRNA vaccine boost. Moreover, the study participants’ median age was 36, which is lower than the global average population. So, the results need to be confirmed by large-scale longitudinal studies with people of different ages.
Now, the researchers will look at how the heterologous vaccination method affects new strains of the SARS-CoV-2 virus. They will see for the first time if this vaccination method can negate the two developing Omicron subvariants BA.4 and BA.5, which are at the root of the recent COVID-19 outbreak in South Africa, adds Qiang Pan Hammarström.
The research was conducted by Karolinska Institutet as part of the ATAC research consortium, which was financed by the European Commission in response to the COVID-19 outbreak. Policlinico San Matteo in Pavia (Italy), The Institute for Research in Biomedicine (Switzerland), the European Commission’s Joint Research Centre and Technische Universitaet Braunschweig (Germany), are all members of the group. The study was also made possible by partnerships involving Shahid Beheshti University of Medical Sciences (Iran), Peking University Health Science Center (China), Stockholm University (Sweden), and Tehran University of Medical Sciences (Iran). The Swedish Research Council and the Knut and Alice Wallenberg Foundation also contributed to the discovery. There are no conflicting interests declared by the researchers.