Fast Five Quiz: COVID-19 Vaccines

Glenn Wortmann, MD


October 15, 2021

The outbreak of the Delta variant of SARS-CoV-2 has led to a surge in breakthrough infections and an increase in severe disease in older individuals with waning immunity, according to a recent study from Israel. These data prompted that country to approve a booster dose of mRNA vaccine to older individuals (≥ 60 years) who had received their second vaccine dose at least 5 months earlier. In late August 2021, Israel began offering boosters to all individuals previously vaccinated with an mRNA vaccine. The Delta variant has more than twice the rate of transmissibility of previously dominant variants and causes a higher rate of breakthrough infections. The amount of viral genetic material may decrease more quickly in fully vaccinated people than in those who are unvaccinated, so it is likely that fully vaccinated people who are infected with the Delta variant will spread the virus for a shorter duration than unvaccinated people will. Despite breakthrough infections, the vaccines still provide the best protection against serious illness and death from COVID-19.

The Alpha, Beta, and Gamma variants also meet the World Health Organization's criteria for variants of concern. The Alpha variant is more transmissible than previous variants, but vaccines are effective at preventing symptomatic COVID-19 infection caused by this variant. The Gamma variant was first documented in Brazil in November 2020. It is not as transmissible as the Alpha or Delta variants, and it is less resistant to vaccination than the Beta variant. The Lambda and Mu variants are currently considered to be variants of interest.

Regardless of variant, the World Health Organization's current position is that it is unclear whether booster doses of COVID-19 vaccines will be required, and if they are, at what periodicity.

Learn more about SARS-CoV-2 variants and COVID-19 vaccines.


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