Certified in Public Health (CPH) Practice Exam

Why must new influenza vaccines be developed annually?

1. Mutations result in new strains of the virus that are not affected by existing vaccines

2. The virus produces enzymes that break down existing vaccines

3. The human body produces enzymes that break down existing vaccines

4. The human body produces antibodies that inactivate the vaccine

The correct answer is: Mutations result in new strains of the virus that are not affected by existing vaccines

New influenza vaccines must be developed annually because of the phenomenon known as antigenic drift, which involves mutations that lead to the emergence of new strains of the influenza virus. These mutations can alter the viral surface proteins, specifically hemagglutinin and neuraminidase, which are the primary targets of the immune response generated by vaccines. As a result, the strains that circulate in the population can differ significantly from those that were used to formulate the previous year's vaccine, leading to decreased effectiveness if the same vaccine is used. This constant change in the virus necessitates that public health officials and vaccine manufacturers monitor circulating strains closely and update the vaccine composition accordingly each year to ensure that it matches the most current prevalent strains. This process maximizes the vaccine's effectiveness in preventing influenza illness, particularly since the virus can cause widespread outbreaks and seasonal epidemics.