The concept of a "less-fatal" case of a disease, like polio or measles, can be better understood by examining the differences between natural infection and vaccination.
Natural Infection: When a person contracts a disease naturally, their body's immune system is exposed to the full strength of the infectious agent. The severity of the illness will vary depending on factors such as the individual's overall health, age, and immune response. In some cases, the infection can be mild or asymptomatic, but in others, it can be severe, leading to complications and even death.
Vaccination: Vaccines work by introducing a weakened or inactivated form of the virus or bacteria into the body. This prompts the immune system to recognize the pathogen and mount a protective response. Vaccines are designed to prime the immune system to respond quickly and effectively if the person is exposed to the actual infectious agent in the future.
Now, let's compare how the two scenarios play out:
For COVID-19: Vaccinated individuals who still get infected with the SARS-CoV-2 virus are generally more likely to experience a milder form of the disease. The vaccine-induced immunity helps the body control the virus more effectively, reducing the viral load and the severity of symptoms. Hospitalization and death rates are significantly lower among vaccinated individuals compared to those who are unvaccinated.
For Polio and Measles: There are vaccines available for both polio and measles that have been highly effective in preventing severe disease. People who are vaccinated and later exposed to the virus are much less likely to develop the full-blown disease. If they do get infected, the symptoms are usually much milder, and the risk of complications is greatly reduced.
However, it's important to note that no vaccine is 100% effective, and breakthrough infections (infections in vaccinated individuals) can still occur. The term "breakthrough" doesn't mean the vaccine has failed; rather, it indicates that the infection has managed to "break through" the immunity provided by the vaccine. Nevertheless, breakthrough infections are usually less severe and less likely to lead to severe outcomes compared to infections in unvaccinated individuals.
Vaccination provides significant benefits on both individual and population levels, as it reduces the risk of severe illness, hospitalization, and death, and also contributes to achieving herd immunity, protecting those who cannot be vaccinated due to medical reasons. It is a crucial tool in public health efforts to control infectious diseases and prevent outbreaks.