<unk>  protects against becoming infected with<unk> . Nearly all of those who do not develop immunity after a single dose develop it after a second dose. When rates of vaccination within a population are greater than 92%, outbreaks of<unk>  typically no longer occur; however, they may occur again if rates of vaccination decrease. The vaccine's effectiveness lasts many years. It is unclear if it becomes less effective over time. The vaccine may also protect against<unk>  if given within a couple of days after exposure to<unk> . The vaccine is generally safe, even for those infected by HIV. Most children do not experience any side effects; those that do occur are usually mild, such as fever, rash, pain at the site of injection, and joint stiffness; and are short-lived. Anaphylaxis has been documented in about 3.5–10 cases per million doses. Rates of Guillain–Barré syndrome, autism and inflammatory bowel disease do not appear to be increased by<unk> tion. The vaccine is available both by itself and in combinations such as the MMR vaccine (a combination with the rubella vaccine and mumps vaccine) or the MMRV vaccine (a combination of MMR with the chickenpox vaccine). The<unk>  is equally effective for preventing<unk>  in all formulations, but side effects vary for different combinations. The World Health Organization (WHO) recommends<unk>  be given at nine months of age in areas of the world where the disease is common, or at twelve months where the disease is not common.<unk>  is based on a live but weakened strain of<unk> . It comes as a dried powder which is mixed with a specific liquid before being injected either just under the skin or into a muscle. Verification that the vaccine was effective can be determined by blood tests. The<unk>  was first introduced in 1963. In that year, the Edmonston-B strain of<unk>  virus was turned into a vaccine by John Enders and colleagues and licensed in the United States. In 1968, an improved and even weaker<unk>  was developed by Maurice Hilleman and colleagues, and began to be distributed, becoming the only<unk>  used in the United States since 1968. About 85% of children globally had received this vaccine as of 2013. In 2015, at least 160 countries provided two doses in their routine immunization. It is on the World Health Organization's List of Essential Medicines. As outbreaks easily occur in under-vaccinated populations, non-prevalence of disease is seen as a test of sufficient vaccination within a population.
Measles vaccine
Typhus vaccine
Polio vaccine
Rabies vaccine
Typhoid vaccine
Hantavirus vaccine
MMR vaccine
Mumps vaccine