👉 Vaccine efficacy and effectiveness are key metrics in vaccine math, often calculated using the formula for relative risk reduction (RRR). RRR is derived from comparing the incidence of disease in vaccinated and unvaccinated groups. For example, if a vaccine reduces disease risk by 90%, the RRR would be \(1 - \frac{\text{Disease rate in vaccinated}}{\text{Disease rate in unvaccinated}}\), which simplifies to \(1 - \frac{1}{1 + \frac{\text{Vaccine efficacy}}{100}}\). This means the vaccine is 90% effective. Herd immunity threshold, another critical concept, is calculated as \(1 - \frac{1}{R \times D}\), where \(R\) is the vaccine efficacy and \(D\) is the basic reproduction number of the disease, indicating the average number of secondary infections one infected person will cause in a fully susceptible population. These calculations help public health officials understand how vaccines protect communities and guide vaccination strategies.
