Examining Our Approach to COVID Vaccines

The race to develop vaccines for SARS-CoV-2 started soon after the COVID-19 pandemic emerged. A significant portion of the initial medications used messenger ribonucleic acid (mRNA) as their vector. In the United States, it was first suggested — or in some cases required — that a two-stage vaccination protocol be used. As expected, the virus mutated, leading to the call for booster vaccinations to address these new strains.

Two papers from the Cleveland Clinic have brought aspects of this approach into question. The first evaluated 39,766 subjects, 20% of whom had previously been infected with COVID-19, while the remainder had been vaccinated with the original two-stage vaccination. The study examined the efficacy of multiple doses. Participants received either the Pfizer or Moderna mRNA vaccines and most completed the two-dose regimen. Individual bivalent booster vaccines were made available to this group starting in August 2021. Among the findings was that the risk of infection increased as the time from the person’s last infection or vaccination increased. In general, the effectiveness was gone or greatly reduced after six months. For participants who had been vaccinated but not previously infected, a booster was associated with lower risk of disease. Of interest was that those who previously had been infected and had received only one dose of the original vaccine had a lower risk of contracting COVID-19 than those who had received two injections.¹

DISEASE RISK INCREASED IN PROPORTION TO THE TIME SINCE A PRIOR DISEASE EPISODE OR VACCINATION 

A second study from the same clinic also examined the efficacy of multiple vaccinations. After evaluating 51,011 subjects, the researchers noted that 41% of study participants reported having at least one previous episode of COVID-19, while more than 83% had received two or more vaccine doses. Among this 83% group, 5% developed the disease during the study. Similar to the findings in the first paper, Shrestha et al² also found that disease risk increased in proportion to the time since a prior disease episode or vaccination. Worth noting is that individuals receiving three doses of the vaccine were more likely to contract COVID-19 than those who had two doses. Additionally, those who had received only one dose were the least likely to experience the disease.²

Among the authors’ conclusions are that for the study participants, having the disease provides better immunity than vaccination, and there is little indication for vaccination within six months of having had active COVID-19.²

If other studies report similar conclusions, the current approach to vaccinations may need to be amended. This becomes especially important now that U.S. Food and Drug Administration officials are recommending yearly mRNA vaccines. It is hoped that appropriate clinical trials will be performed to provide answers on how best to employ these, or other, vaccines.

Thomas G. Wilson Jr., DDS
Editor in Chief
twilson@belmontbusinessmedia.com

References

1. Shrestha NK, Shrestha P, Burke PC, Nowacki AS, Terpeluk P, Gordon SM. Coronavirus disease 2019 vaccine boosting in previously infected or vaccinated individuals. Clin Infect Dis. 2022;75:2169–2177.
2. Shrestha NK, Burke PC, Nowacki AS, Simon JF, Hagen A, Gordon SM. Effectiveness of the coronavirus disease 2019 (COVID-19) bivalent vaccine. Available at: https://www.medrxiv.org/content/10.1101/2022.12.17. 22283625v1.full-text. Accessed March 14, 2023.

From Decisions in Dentistry. April 2023;9(4):6.