Vaccination policy is the health policy a government adopts in relation to vaccination. The vaccine had also reduced mortality among those who were infected after vaccination. These incidents reduced public confidence in polio vaccine leading to a drop in vaccination rates. The terms inoculation, vaccination, and immunization are often used synonymously. Private institutions might require annual influenza vaccination. Neutralising antibodies also play a role in active immunisation by vaccination. Some countries require the varicella vaccination or an exemption before entering elementary school. The incidence of hepatitis A where widespread vaccination has been practised has decreased dramatically. Prevention includes avoiding risk factors and HPV vaccination. People with COPD are recommended by a number of guidelines to have a pneumococcal vaccination. Diphtheritic croup is extremely rare in countries where diphtheria vaccination is customary. Boat Memory died following a smallpox vaccination. This scar must be distinguished from that of smallpox vaccination, which it may resemble. Individuals can become immune by recovering from an earlier infection or through vaccination. In 1903 Shaw joined in a controversy about vaccination against smallpox.