COVID-19 vaccine insights: The news beyond the headlines

Although mRNA vaccines seem novel, they have been in development for more than 30 years.

Data from trials in Israel that became available early in 2021 showed that, in mRNA-vaccinated adults, mechanical ventilation rates declined strikingly, particularly in patients > 70 years of age.^15,16 This finding was corroborated by data from a surveillance study of multiple US hospitals, which showed that mRNA vaccines were > 90% effective in preventing hospitalization in adults > 65 years of age.¹⁷

Data published in May 2021 showed that the Pfizer-BioNTech and Moderna vaccines were 94% effective in preventing COVID-19-related hospitalization.¹⁸ During the end of the Delta wave of the pandemic and the emergence of the Omicron variant of SARS-CoV-2, unvaccinated people were 5 times as likely to be infected as vaccinated people.¹⁹

In March 2022, data from 21 US medical centers in 18 states demonstrated that adults who had received 3 doses of the vaccine were 94% less likely to be intubated or die than those who were unvaccinated.¹⁶ A July 2022 retrospective cohort study of 231,037 subjects showed that the risk of hospitalization for acute myocardial infarction or for stroke after COVID-19 infection was reduced by more than half in fully vaccinated (ie, 2 doses of an mRNA vaccine or the viral vector [Janssen/Johnson & Johnson] vaccine) subjects, compared to unvaccinated subjects.²⁰ The efficacy of the vaccines is summarized in TABLE 1.^21-24

Even in patients who have natural infection, several studies have shown that ­COVID-19 vaccination after natural infection increases the level and durability of immune response to infection and reinfection and improves clinical outcomes.^9,20,25,26 In summary, published literature shows that (1) mRNA vaccines are highly effective at preventing infection and (2) they augment immunity achieved by infection with circulating virus.

Breakthrough infection. COVID-19 mRNA vaccines are associated with breakthrough infection (ie, infections in fully ­vaccinated people), a phenomenon influenced by the predominant viral variant circulating, the level of vaccine uptake in the studied population, and the timing of vaccination.^27,28 Nevertheless, vaccinated people who experience breakthrough infection are much less likely to be hospitalized and die compared to those who are unvaccinated, and vaccination with an mRNA vaccine is more effective than immunity acquired from natural infection.²⁹

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