Injected measles vaccine stimulates a significantly stronger immune response than inhaled vaccine, a new study reports.
In a trial funded by the Bill and Melinda Gates Foundation, researchers randomly assigned 2004 Indian children aged 9 to 12 months who were eligible for a first dose of measles vaccine to receive a single dose of either injected (1003 children) or inhaled (1001 children) vaccine. At 91 days of follow-up, children who got the injections showed markedly higher rates of seropositivity for antibodies than recipients of the aerosolized vaccine. None of the children contracted measles, and adverse events in the 2 groups were similar.
Although 1956 (97.6%) of all the children were followed to day 91, thawed specimens precluded evaluating outcome data for 331 children. In the per-protocol population, researchers were able to evaluate data on 1560 (77.8%) of 2004 children. At day 91 in this population, 662 of 775 children (85.4%) who received the aerosol vaccine were seropositive for antibodies compared with 743 of 785 children (94.6%) who received injections. The full-analysis data set yielded similar results: 85.4% seropositivity among children who received inhaled vaccine and 94.7% among recipients of injected vaccine.
The study helps clarify the immunogeneticy of aerosolized measles vaccine, for which data have been inconsistent. The researchers conclude that the inhaled vaccine is immunogenic but falls short of injected vaccine in rates of antibody seropositivity.
Moreover, although the inhaled vaccine has the advantage of being needle free, it can’t deliver multiple vaccines in 1 dose as can the injected measles-mumps-rubella and measles-mumps-rubella-varicella vaccines. Injection is the prevailing delivery method in the United States and is considered the gold standard for measles immunization.
The Centers for Disease Control and Prevention (CDC) has reported 166 measles cases in 19 states and the District of Columbia so far this year (as of April 24). Most cases are part of a multistate outbreak linked to a California amusement park. In 2014, the CDC reported 668 cases in 27 states, the largest number since 2000, when measles was considered to be eliminated in the United States.