Scientists Measured Whether Individuals Who Had Been Vaccinated with Anti-HPV

Scientists measured whether individuals who had been vaccinated with anti-HPV vaccines (Gardasil and Cervarix) had detectable levels of anti-HPV antibodies in their blood many years after receiving the vaccines. The data are shown here. Based only on these data, which of the following policy recommendations would you make to the United States Center for Disease Control and Prevention (the agency that sets vaccination schedules) regarding anti-HPV vaccines?

A) Individuals who are vaccinated with Cervarix will never need a "booster" shot even 30 years after initially being vaccinated.
B) Gardasil protects against HPV-related cancer better than Cervarix, so individuals should be vaccinated with Gardasil and not Cervarix.
C) After many years, Cervarix is about twice as effective at preventing HPV-related cancer than Gardasil, so individuals should be vaccinated with Cervarix and not Gardasil.
D) If people are vaccinated with Gardasil, they may need a "booster" shot in the future to maintain high levels of protection from HPV-related cancers.