Final answer:
To achieve herd immunity without a vaccine, a significant portion of the population must be immune due to vaccination or past infection. Herd immunity protects those who are unvaccinated or cannot be vaccinated, but it requires maintaining high vaccination rates.
Step-by-step explanation:
If you want to achieve herd immunity without the benefit of a vaccine, the correct answer is b. A certain percentage of the population must be immune, either through vaccination or prior infection. Herd immunity protects the whole community, including those who are unvaccinated or unable to receive vaccines, by ensuring that enough people are immune to prevent the disease's spread. Consequently, those who are susceptible are less likely to come into contact with the disease. However, it is important to note that herd immunity can be compromised if the number of vaccinated individuals drops too low, leading to outbreaks of diseases like whooping cough and measles.
Immunization has been instrumental in preventing millions of deaths each year and achieving the eradication of certain diseases. High levels of immunization in a population create a protective barrier against the spread of contagious diseases, illustrating the effectiveness and importance of vaccines in public health.