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Most healthy adults who have followed recommendations for measles vaccination are not in need of additional vaccination, despite recent outbreaks in certain parts of the US, according to experts.

“A complete two-dose measles vaccination provides 97% protection for a lifetime,” said William Schaffner, MD, professor of medicine in the Division of Infectious Diseases at Vanderbilt University, Nashville, Tennessee, in an interview. “Measles infections that occur despite having received two doses of vaccine are unusual and, when they occur, usually are rather mild,” he added.

“The only measles vaccine available in the US is MMR [measles, mumps, and rubella]; there is no stand-alone measles vaccine,” Schaffner told Medscape Medical News.

What the CDC Says

The CDC currently recommends two doses of the MMR vaccine for all children, with a first dose at age 12-15 months and a second at age 4-6 years.

One high-risk group for whom the CDC recommends MMR vaccination is young adults at college and other post-high school institutions who lack evidence of immunity — they should receive two doses at least 28 days apart.

Other adults without evidence of immunity should receive two doses at least 28 days apart if they are in high-risk settings, such as healthcare or international travel. Otherwise, low-risk, healthy adults without evidence of immunity should receive at least one dose of MMR, according to the CDC.

The evidence of immunity against MMR is defined by the CDC as at least one of the following: Documentation of adequate vaccination, laboratory confirmation of disease, laboratory evidence of immunity against MMR, or birth before 1957.

However, certain groups including pregnant women, individuals with immunocompromising conditions, and those with severe allergies to any of the vaccine components should not receive an MMR vaccine, according to the CDC.

Clinical Perspective

Prior to 1989, a single dose of measles vaccine was standard practice, said Shirin A. Mazumder, MD, an infectious diseases specialist in Memphis, Tennessee, in an interview.

“One dose of the measles vaccine is approximately 93% effective, and two doses of the vaccine increase the level of protection to 97%,” she said.

Individuals born after 1957 and vaccinated between 1963 and 1967 likely received a different version of the current MMR vaccine that was inactivated and less effective, Mazumder noted. “Individuals vaccinated between 1963 and 1967 can consider receiving an additional vaccine dose to increase their level of protection,” she said.

The risk assessment for measles vaccination, as with other vaccinations, should be an open discussion between clinicians and their adult patients, Mazumder told Medscape Medical News.

“In otherwise healthy adults, the measles vaccine is well tolerated and highly effective,” she said. Some adverse effects associated with the vaccine include fever and transient rash, reported in 5% or fewer of adult recipients, as well as transient lymphadenopathy and arthralgias, reported in approximately 20% and 25% of recipients, respectively.

ACIP’s Impact

“The dismissal of all the sitting members of Advisory Committee on Immunization Practices (ACIP) may have a damaging impact on public health in this country and dismantle a transparent process that has been in place for a long time and saved countless lives,” said Mazumder. “Traditionally, ACIP was made up of an independent and diverse group of advisors, and the previous meetings were open to the public with a very transparent process,” she told Medscape Medical News.

“Physicians rely on the decisions made by ACIP to help guide the recommendations passed on to their patients, and there is a concern that the ongoing changes will make it harder for clinicians to care for their patients,” she said. Decisions made by ACIP shape immunization schedules and also impact insurance coverage, which affects public access to vaccines, Mazumder added.

Overall, the potential impact of the newly reconstituted ACIP on adult measles vaccination, and on vaccination in general, remains to be seen, Schaffner told Medscape Medical News. “We need to give this some time and be prepared to continue to give our good advice to our patients,” he said.

Mazumder reported no financial conflicts of interest. Schaffner reported no financial conflicts of interest.