By Richard L. Wasserman, M.D., Ph.D.
By the time you read this, the window of risk for having contracted measles from a fellow celebrant during a Pesach holiday trip will have just closed. If you are not sick, you are OK, unless you’ve spent time with someone who has come down with measles. Because the current epidemic has involved Jewish communities, being fully informed about the disease can help protect you, your family and the community.
Measles presents with fever (maybe as high as 105 degrees), malaise, cough, runny nose and conjunctivitis, followed by a characteristic rash. People are contagious from four days before until four days after the appearance of rash. The incubation period is usually eight to 12 days, with the time from exposure to the appearance of rash averaging 14 days. Measles can be a serious illness with a 1/1000 rate of brain inflammation, and a fatality rate of 1-2/1000. Children under age 5, pregnant women and adults older than 20 years are at increased risk of complications from measles infection. There is no specific treatment.
Measles is one of the most highly contagious viral illnesses, infecting at least 90 percent of those who are exposed. The measles virus remains in the air of a room for two hours after a contagious person departs. Measles is also one of the most easily preventable infections because current vaccine recommendations confer protection to at least 97 percent of people. Measles vaccine should be given at 12-15 months of age, and again between ages 4-6. In fact, if the schedule is missed, the first dose can be administered at any time, and the second dose can be given as soon as four weeks after the first. Two doses of vaccine appear to provide lifelong immunity.
When the vaccination rate in a community is 93 percent or greater, the community benefits from herd immunity. Herd immunity means that enough protected community members exist, so the chance of an infected person passing his or her contagion to another community member is very low, and serial illness leading to an epidemic does not occur. Herd immunity is what protects babies less than 1 year of age who have not been immunized and people immunocompromised due to cancer, autoimmune disease or immunosuppressive therapy used to treat those diseases.
Because measles is so contagious and natural infection provides lifelong immunity, people born before 1957 (the introduction of the first vaccine) are presumed to be immune. The vaccine used from 1957 to 1967 was a killed virus vaccine that required three doses and was less effective than current vaccines. Most children who received the killed vaccine were revaccinated with the live virus vaccine. From 1967 to 1989, only one dose of vaccine was recommended. Many adults don’t have their vaccination records. The following assumptions are in place for those born in the United States.
• Age 62 or older: presumed to have acquired immunity through natural infection.
• Ages 36-62: received at least one dose of vaccine, and might have received two doses. Under normal circumstances, when there is herd immunity and the risk of exposure is very low, there are no concerns. The Centers for Disease Control (CDC) makes no recommendations. However, vaccination is recommended for health care personnel, students in postsecondary educational institutions, international travelers and household or close personal contacts of immunocompromised persons with no evidence of immunity to measles (i.e., no documentation of having received two doses of vaccine).
• Age 36 or younger: presumed to have received two doses of measles vaccine and are protected.
Adults at increased risk of exposure and who are uncertain of their measles immunity should receive one or two doses of MMR vaccine. Alternatively, measles immunity can be measured with a blood test. If there is measles immunity, no additional vaccine is needed.
Significant vaccine side effects beyond injection site pain and low-grade fever are rare, and usually resolve on their own in a few days. It is clear, based on an overwhelming body of evidence, that the MMR vaccine does not cause autism.
Because some Jewish communities in the Northeast are in the middle of the measles epidemic, and because travel is common in our communities, adults with uncertain measles immunity, and who consider themselves to be at increased risk of exposure, should take steps to ensure that they are protected.
Richard L. Wasserman is an allergist/immunologist practicing in North Dallas.