Under the Microscope with David Weber: Update on COVID-19 Vaccines

Author: David Weber, MD, MPH, FSHEA, FIDSA, FMSM (London)

As of 30 November 2021, the United States has had 48,525,271 cases of COVID-19 leading to 779,859 deaths. In 2020, COVID-19 was the third leading cause of death in the United States, ranking only behind cardiovascular disease and cancer.¹ Likely COVID-19 will also be the third leading cause of death in the United States again in 2021. The University of Washington projects estimates that by 1 March 2022, total deaths in the United States due to COVID-19 will be ~1,024,000. Receipt of a COVID-19 vaccine is the most effective preventive strategy to prevent COVID-19.  This blog will review COVID-19 vaccines with a focus on the rationale for booster doses, vaccination of persons who have had COVID-19, and vaccine use in children 5 years and older.

At the present time, there are three COVID-19 vaccines available in the United States either approved or authorized by the U.S. Food and Drug Administration (FDA) and recommended by the U.S. Centers for Disease Control and Prevention (CDC): Pfizer-BioNTeck (available for ages 5+), Moderna (available for ages 18+) and Johnson & Johnson’s Janssen (available for ages 18+).² Recently, booster doses of Pfizer and Moderna were authorized for all adults by the FDA. The CDC currently recommends that all persons older than 18 years of age receive a booster dose.

Additional details on current CDC COVID-19 vaccine recommendations are summarized in the table below adapted from the CDC.

COVID-19 vaccines have been determined to be both safe and highly effective. Booster doses have been demonstrated to substantially increase the antibody levels in persons who have received a primary vaccine series. Further, two studies from Israel have both demonstrated that within two weeks of receiving a booster, the risk of developing symptomatic COVID-19 and severe COVID-19 is substantially lower. The study by Bar-On and colleagues showed that at least 12 days after the booster dose, the rate of confirmed infection was lower in the booster group than in the non-booster group by a factor of 11.3 (95% confidence interval [CI], 10.4 to 12.3); the rate of severe illness was lower by a factor of 19.5 (95% CI, 12.9 to 29.5).³  The study by Barda and co-workers showed that at least 7 days after a booster dose compared with receiving only two doses at least 5 months ago, was estimated to be 93% for admission to hospital, 92% for severe disease, and 81% (44 vs seven events; 59–97) for COVID-19-related death.  Thus, all eligible persons should receive a booster dose.⁴

Two studies have now demonstrated that persons with natural protection (i.e., persons who have had COVID-19) have a substantially higher risk of reinfection than fully vaccinated persons. Cavanaugh and colleagues using a case-control design reported that Kentucky residents who were not vaccinated had 2.34 times the odds of reinfection compared with those who were fully vaccinated (odds ratio [OR] = 2.34; 95%CI=1.58–3.47).⁵  Bazio et al. using data collected from 187 hospitals reported that among COVID-19–like illness hospitalizations among adults aged ≥18 years whose previous infection or vaccination occurred 90–179 days earlier, the adjusted odds of laboratory-confirmed COVID-19 among unvaccinated adults with previous SARS-CoV-2 infection were 5.49-fold higher than the odds among fully vaccinated recipients of an mRNA COVID-19 vaccine who had no previous documented infection (95% confidence interval = 2.75–10.99).⁶  Thus, all persons who have had COVID-19 should receive a COVID-19 vaccine series when no longer infectious.

Vaccinations for Children

COVID-19 vaccines are now available for children ages 5 years and older. As with adults, COVID-19 vaccines have been found to be highly effective and safe in children. In recent months, the number and percent of children developing COVID-19 have increased.  Although children, in general, have experienced less severe disease than adults, severe hospitalizations and deaths may occur.⁷  Adolescent hospitalization rates and mortality are substantially higher from COVID-19 compared with influenza.⁸  As with adults, infected children may develop COVID-19 “long haulers” syndrome with symptoms (e.g., brain fog, fatigue, etc.) lasting months.

Finally, current vaccines, in the era of the Delta variant, remain highly effective in preventing symptomatic COVID-19 and even more effective in preventing hospitalizations and deaths (CDC).  Booster doses have been demonstrated to substantially increase the antibody levels in persons who have received a primary vaccine series.  The U.S. now ranks 51^st in the world in the level of COVID-19 vaccine coverage for its citizens (NY Times).  Increasing COVID-19 vaccine uptake is crucial to protecting individuals and reducing the risk of SARS-CoV-2 transmission.

Additional Recommendations for Immunocompromised People:

• Additional primary dose: moderately to severely immunocompromised people who are 12 years and older and received a Pfizer-BioNTech primary series or 18 years and older and received a Moderna primary series should receive an additional primary dose of the same vaccine at least 28 days after their second dose.
• Booster dose: moderately to severely immunocompromised people who are 18 years of age and older and received a Pfizer-BioNTech or Moderna primary series are also eligible for a booster dose at least 6 months after their additional primary dose, using any of the three COVID-19 vaccines. Immunocompromised people who received a J&J/Janssen vaccine are not recommended to receive an additional primary dose but should receive a booster dose at least 2 months after their initial dose, using any of the three COVID-19 vaccines.

Stay up-to-date on how COVID-19 vaccinations are trending in the United States here.