A novel COVID-19 vaccine uses mRNA to present viral proteins along with an adjuvant. Which mechanism explains why a second dose is typically administered weeks after the first?

💡 Explanation

The second dose boosts the adaptive immune response, specifically B cell affinity maturation, because it allows B cells to further refine their antibody specificity for increased binding strength to the antigen. Therefore, the second dose increases the overall effectiveness of the vaccine, rather than simply preventing immediate allergic reactions.

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