What does "vaccine efficacy" refer to?

What does "vaccine efficacy" refer to?

• A. The number of vaccines administered
• B. The percentage increase in disease incidence
• C. The percentage reduction in disease incidence in a vaccinated group compared to an unvaccinated group
• D. The cost-effectiveness of a vaccine

Answer: (C)

Vaccine efficacy is best defined as the percentage reduction in disease incidence among vaccinated individuals compared to those who are unvaccinated. This measure is critical for understanding how well a vaccine works in real-world conditions. It objectively quantifies the vaccine's ability to prevent disease by comparing the incidence rates between the two groups, thus providing insights into its protective effects. When assessing a vaccine's performance, effectiveness in preventing the targeted disease is paramount, and efficacy provides a clear metric for this. Therefore, a high efficacy rate indicates that the vaccine is effective at reducing the incidence of the targeted disease among those who receive it, which is instrumental for public health decision-making. Other options address different aspects related to vaccines, such as operational aspects (number of vaccines administered) or economic considerations (cost-effectiveness). However, they do not specifically encapsulate the scientific measurement of how effective a vaccine is at preventing disease, which is the essence of vaccine efficacy.

Vaccine efficacy is best defined as the percentage reduction in disease incidence among vaccinated individuals compared to those who are unvaccinated. This measure is critical for understanding how well a vaccine works in real-world conditions. It objectively quantifies the vaccine's ability to prevent disease by comparing the incidence rates between the two groups, thus providing insights into its protective effects.

When assessing a vaccine's performance, effectiveness in preventing the targeted disease is paramount, and efficacy provides a clear metric for this. Therefore, a high efficacy rate indicates that the vaccine is effective at reducing the incidence of the targeted disease among those who receive it, which is instrumental for public health decision-making.

Other options address different aspects related to vaccines, such as operational aspects (number of vaccines administered) or economic considerations (cost-effectiveness). However, they do not specifically encapsulate the scientific measurement of how effective a vaccine is at preventing disease, which is the essence of vaccine efficacy.