COVID-19 vaccine insights: The news beyond the headlines

Boosters and vaccine mix-and-match

As the COVID-19 pandemic persists, with new variants of concern emerging, it has also become clear that immunity wanes. In July 2021, the first report was published after a cluster of breakthrough infections occurred in a town in Massachusetts.⁴² There was no recommendation, at the time, for a booster; the Delta variant was the predominant circulating strain. In this outbreak, there were 469 cases, 74% of which were in people who had received 2 doses of an mRNA vaccine.⁴² Five patients were hospitalized; none died.⁴² A key takeaway from this outbreak was that vaccination prevented death, even in the face of fairly wide breakthrough infection.

Vaccination with an mRNA vaccine is more effective than immunity acquired from natural infection.

Newer data show that, although vaccine effectiveness against hospitalization was greater than 90% for the first 2 months after a third dose, it waned to 78% by 4 months.⁴³ Published data, combined with real-world experience, show that boosters provide additional reduction in the risk of death and hospitalization. This has led to a recommendation that all patients ≥ 5 years of age receive a booster.^19,26,43-48 The CDC now recommends that people who are ages 12 years and older receive a bivalent booster (containing both wild-type and Omicron-variant antigens) ≥ 2 months after their most recent booster or completed series.

Future booster recommendations will consider the durability of the immune response over time (measured against the original immunizing virus) and the mutation rate of the virus.⁴⁹

Given the limited supply of vaccine early in the pandemic, and the potential for future limitations, there was early interest in studying so-called mix-and-match SARS-CoV-2 vaccination—that is, receiving one product as a first series and then a different product as a booster, also known as heterologous booster vaccination. Although it is preferred that the 2 doses of the primary series be of the same vaccine product, studies that have examined this question support heterologous boosting as an acceptable approach to protective immunity⁵⁰ (TABLE 2⁵¹).

Vaccination in special populations

Three groups of patients have unique host characteristics that are important to consider when providing COVID-19 vaccination in your practice: pregnant patients, children, and patients in the broad category of “immunocompromised status.”

Continue to: Pregnant patients