An article from NBC news questions if the best strategy against the Omicron variant of Covid-19 is to use existing boosters of the existing Covid-19 vaccine or to wait for Omicron-specific vaccines to be produced instead.

This is due to concern that using pre-existing Covid-19 vaccines as boosters, which were produced to target the original strain of Covid-19 might in fact lead to a weaker immune response against different versions of the virus, a phenomenon described by immunologists as “original antigenic sin”.

Original antigenic sin in other vaccinations?

As it is difficult to ascertain if this phenomenon will occur or if an Omicron-specific vaccine is even necessary, we decided to conduct research on older vaccines such as the influenza vaccine to determine the validity of “original antigenic sin” claims. A peer reviewed article from the Journal of Clinical and Vaccine Immunology found that antibody responses to the H1N1 influenza virus vaccine were reduced in people who had recently taken the seasonal influenza jab, showing evidence of the “original antigenic sin” effect in prior vaccinations.

Another article, from the Journal of Immunology discovered that the specificity and the quality of immune responses against novel strains of influenza is often diminished in individuals who have been repeatedly immunized (either by vaccination or recurrent infections). The potential for each flu vaccine or infection to induce original antigenic sin thus remains, hence the need for annual flu vaccinations.

The phenomenon has been detected in the HPV vaccine. Studies from the American Society for Microbiology described how the HPV vaccine, which is constantly being improved upon to target the different types of HPV as eliciting diminished responses in people who had been inoculated with earlier versions of the vaccine.

Do multiple boosters of the original vaccine make future versions of the vaccine less effective?

Based on the evidence found, it is true that original antigen sin has been detected in other vaccines, making future vaccines less effective. However, this does not mean that one should not opt for the Covid-19 booster shot. As the booster has proven efficacy against current strains of the virus, choosing to wait for a vaccine that is created specifically to target the Omicron variant is a high risk strategy.

The high transmission rate of the delta variant is still a cause for concern, with Dr Anthony Fauci, director of the National Institute for Allergy and Infectious Disease stating that booster shots are very likely to provide cross protection against a wide range of Covid-19 variants.

With all this in mind, while multiple boosters of the original vaccine are likely to make future specified vaccines less effective, forgoing current vaccines while waiting for new versions to be developed is not advised, with it being risky should one be infected by Covid-19 before being inoculated by the future vaccine.

In conclusion, the claim that multiple boosters of the original vaccine might make future vaccine versions less effective is likely true, due to the phenomenon described by immunologists as “original antigenic sin”.