Special Report: Vaccines in Development Part 5: Potential emerging vaccine candidates and other considerations

Section 5: Other Promising Vaccine Candidates and Considerations

Messenger RNA (mRNA) vaccines have offered a novel methodology in the context of COVID-19, including the Pfizer/BioNTech1 and Moderna2 vaccines. Rather than placing a weak or inactivated germ into the human body, mRNA vaccines  utilize host cells to make a protein that triggers an immune response and, in turn, produces antibodies to prevent future infection.3,4 Despite the common misconception, mRNA vaccines never enter cell nuclei and are therefore unable to alter host DNA in any capacity. These mRNA vaccines have been under development for decades.5 University of Oxford/AstraZeneca6 and Johnson & Johnson/Janssen Pharmaceuticals7 have focused on adenovirus vector approaches to the vaccine, which also show promise in preventing COVID-19. Another candidate vaccine uses recombinant vesicular stomatitis virus vector (V591),8 which is being developed by Merck Sharpe and Dohme, and the International AIDS Vaccine Initiative.9,10 This approach is similar to Erverbo, the recombinant stomatitis virus-vectored Ebola Zaire live vaccine, also developed by Merck Sharp and Dohme. Beginning on August 27, 2020, this Phase 1/2 randomized, double-blind, placebo-controlled, dose-ranging trial sought to evaluate safety, tolerability, and immunogenicity of single- and double-dose V591 administered via intramuscular injection. Merck Sharp and Dohme also began a Phase 1 trial for dose-ranging of V590 on October 29, 2020, which includes a single dose via intramuscular injection (5.00 x 105pfu/mL, 2.40 x 106pfu/mL, 1.15 x 107pfu/mL, 5.55 x 107pfu/mL).11 Despite the promising vaccine candidates being authorized and developed, there are still several barriers that must be confronted to ensure broad public safety. Not only is resource allocation essential, but we must be cognizant of the health disparities that exist and ensure that we do not further perpetuate them. Prioritizing vaccine allocation based on race/ethnicity is an ethically and legally contentious topic,11 but people of color are disproportionately represented among COVID-19 cases and deaths.12,13 People of color are also underrepresented among clinical trials. After frontline healthcare workers and residents of long-term living facilities are vaccinated,14 the next group will need to be carefully prioritized. Further, vaccines are likely to face scrutiny by a subgroup of people. A Pew Research Center survey from September 2020 found that nearly 49% of respondents ‘definitely or probably would not’ get vaccinated,15 though this was earlier in vaccine development. With multiple vaccines reaching the market by Summer 2021, information will continue to be collected to ensure long-term tolerability, absence of adverse events, and control of any allergic reactions. With 16,897,911 total cases and 309,880 deaths due to COVID-19 in the U.S. as of December 18, 2020,16 it is critical that states and the general public view vaccination from an apolitical, scientific perspective. This will need to be supplemented by patient education and culturally-competent practice that understands the mistrust felt toward healthcare professionals and pharmaceutical companies, particularly among people of color.17, 18

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