The correct answer is option 4, "Vaccination of children". The `Mission Indradhanush` campaign in India focuses on improving the coverage and reach of vaccination for children. The goal is to ensure that every child in the country is protected against seven vaccine-preventable diseases, namely diphtheria, pertussis, tetanus, polio, measles, tuberculosis, and hepatitis B. This campaign was launched in 2014 as a part of the government`s efforts to increase immunization rates and reduce child mortality. Under this campaign, special vaccination drives are conducted in high-priority districts where immunization rates are low, and efforts are made to reach out to children who have not been vaccinated or are partially vaccinated. This initiative plays a crucial role in safeguarding the health and well-being of children in India.