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This message is being sent to the health alert network, local public health officers, Tribal health directors, local public health department nurses, and infection preventionists.
Wisconsin DHS Health Alert #73: Early MMR Vaccination for Infants in Measles Outbreak-Affected Communities
Bureau of Communicable Diseases
November 3, 2026
Key points
- Wisconsin's multi-county measles outbreak that began in August 2026 continues to expand, and additional cases of measles associated with out-of-state travel have been detected in new areas of Wisconsin. As of November 3, there have been 429 cases and eight hospitalizations associated with the outbreak.
- MMR vaccine is strongly recommended for all children starting at age 12 months. Due to the current outbreak, DHS also recommends MMR vaccine for infants aged 6-11 months if they are members of a family or community that is likely to be exposed to measles.
- Because early vaccination has potential disadvantages, giving MMR before age 12 months is not recommended for every child in Wisconsin or for every child in any one county. In this guidance, DHS is sharing the recommended approach for determining which infants should receive early MMR, which may be subject to change.
Background
Wisconsin is having its largest measles outbreak in more than 35 years. Since August, DHS has reported 429 confirmed measles cases in 11 counties. Reported case counts likely understate how far measles has spread, because not everyone who gets sick seeks care or is tested.
Nearly all cases have occurred in people who were unvaccinated. To date, measles transmission has been concentrated in close-knit communities and social networks where vaccination coverage is low, primarily within some Plain (Amish and Mennonite) communities.
Infants are especially vulnerable to measles. In U.S. surveillance from 2001 to 2022, infants younger than 12 months had significantly higher odds of complications, hospitalization, and severe disease than children aged 5–19 years. Children younger than 5 years, pregnant people, and people with weakened immune systems are also at increased risk of severe complications, including pneumonia, encephalitis, and death. Infection in infancy also carries a higher risk of subacute sclerosing panencephalitis (SSPE), a rare complication that is always fatal and appears years later.
Antibodies passed from the mother should not be counted on to protect infants. In settings where measles has been eliminated, most infants have no protection by about 3 months of age. Without an early dose, most infants stay unprotected until the routine MMR dose at 12–15 months.
Early MMR vaccination is recommended for infants exposed to settings where measles is spreading. Two doses of MMR are about 97% effective at preventing measles. ACIP and the American Academy of Pediatrics (AAP) recommend two routine MMR doses, at 12–15 months and at 4–6 years of age, a schedule developed to maximize the number of children who have immunity by the time they start school. ACIP also recommends one early MMR dose for infants aged 6–11 months before international travel and during measles outbreaks.
The decision to administer MMR vaccine to infants younger than 12 months of age is generally a balance between the infant's likelihood of exposure to measles and the limitations of an early dose. An early dose is safe: adverse events are no more frequent than after doses given at older ages. However, it is less effective than a dose given later, and some studies suggest that fewer infants develop an antibody response, and the estimated effectiveness of a dose given before 9 months is about 58%, compared with about 83% for doses given at 9 months or older. Several studies have also linked a first dose before 9 months to lower antibody levels after later doses. The clinical significance of this finding is uncertain.
At this time, DHS recommends early MMR for infants aged 6-11 months whose families are likely to be exposed to measles. In the current outbreak, measles has spread mainly through household, family, and social connections, not through sustained, generalized community transmission. Early vaccination is therefore not currently recommended for all infants in Wisconsin, or all infants in any county. Local health departments are conducting case investigations and contact tracing, so they are best positioned to identify the families that meet the criteria below. Clinicians who receive requests for an early dose from families outside these criteria should use shared decision-making and may contact their local health department for help assessing exposure risk. If DHS and local health departments determine that there is generalized community spread of measles, with cases routinely occurring outside known transmission chains, DHS will broaden this recommendation and notify clinicians of the affected areas.
Recommendations for clinicians
1. Which infants should receive an early MMR dose?
- For this guidance, a measles outbreak is three or more related cases, linked by a chain of transmission or by shared time and place of exposure, with at least one case confirmed by laboratory testing.
- During an outbreak, DHS recommends one early MMR dose for infants aged 6–11 months who are significantly likely to be exposed to measles, not necessarily for all infants in a geographic area. Give the early dose in any of the following circumstances:
- The infant lives with a person who has confirmed or probable measles, or with a person in measles quarantine. If the infant was exposed within the past 6 days, manage the infant first under Section 5 (post-exposure management).
- The infant, or a household member without evidence of immunity, has regular or planned contact with a family or community affected by a current measles outbreak (for example, gatherings, shared childcare, or travel).
- The infant's family belongs to a close-knit community or social network in which measles is spreading, as identified by the local health department based on cases or exposures in that network, not on religious or cultural affiliation alone.
- The infant resides in a jurisdiction where DHS and local health departments have determined there is generalized community spread of measles (that is, an area with cases routinely occurring outside known transmission chains). DHS will notify clinicians of any affected areas.
- Local health departments identify families who meet these criteria through case investigation and contact tracing. Clinicians may contact their local health department to help assess an individual family's exposure risk.
- Separately from any outbreak, ACIP and AAP recommend one MMR dose before international travel for all infants aged 6–11 months.
2. Clinicians should counsel families about the benefits and limitations of giving MMR early.
- For infants who meet the criteria above, recommend the early dose and counsel families on its benefits and limits. If a family requests an early dose for an infant outside these criteria, use shared decision-making.
- Points to discuss with families:
- Most infants lose protective maternal antibodies by about 3 months of age. Without an early dose, most infants stay susceptible until the routine dose at 12–15 months.
- Infants with measles are at the highest risk of serious complications, including pneumonia, encephalitis, hospitalization, death, and subacute sclerosing panencephalitis (SSPE), a fatal complication that appears years later.
- The early dose is well tolerated. Adverse events are no more frequent than after doses given at older ages. The most common reactions are fever and rash 1–2 weeks after vaccination. Febrile seizures follow about 1 in 3,000–4,000 MMR doses, usually 6–14 days after vaccination and have no lasting effects.
- An early dose may give incomplete protection. In a 2019 meta-analysis, the estimated effectiveness of a dose given before 9 months was about 58%. In studies that compared age groups directly, effectiveness was about 51% for doses before 9 months and 83% for doses at 9 months or older.
- An early dose may blunt the immune response to the full 2-dose series. Multiple studies have linked a first dose before age 9 months to lower antibody levels after later doses. The clinical significance is uncertain.
- No vaccine is 100% protective. Infants who received an early dose, and children and adults with one or two doses, can still get measles, especially after close or prolonged household exposure. Measles in vaccinated people may be mild or atypical. Families should keep avoiding known exposures. After an exposure, they should call ahead about any fever or rash, whatever their vaccination status.
3. An early MMR dose does not count toward the routine childhood series.
- A child who received an early dose needs two more doses: one at 12–15 months, at least 28 days after the early dose, and another at least 28 days after that. If the child is still at risk of exposure, give the first of these doses at 12 months.
- MMRV should not be given before age 12 months and is not appropriate to use for the early dose.
4. Children aged 1–3 years at increased risk of exposure should receive their second MMR dose now.
- Children aged 1–3 years who meet the criteria in Section 1 and have received one MMR dose should get a second dose now if at least 28 days have passed since the first. This dose counts as the routine second dose, so no dose is needed at age 4–6 years.
- For other children aged 1–3 years, the second dose is not needed until age 4–6 years. An earlier second dose is acceptable if at least 28 days have passed since the first. It also counts as the routine second dose.
- For all infants, including those who do not meet the early-dose criteria, the best protection is making sure parents, siblings, caregivers, and other household members have evidence of measles immunity.
5. Post-exposure management of infants
- Measles exposure means sharing indoor airspace with an infectious person or entering that space up to two hours after the person left.
- An early dose is not evidence of immunity. Manage any exposed infant younger than 12 months as susceptible, including infants who already received an early dose.
- ACIP and AAP recommend immune globulin (IG) for every exposed infant younger than 12 months. The intramuscular dose (IGIM) is 0.5 mL/kg (maximum 15 mL), given within 6 days of exposure:
- Infants younger than 6 months: give IGIM.
- Infants aged 6–11 months: MMR may be given instead of IG if it can be given within 72 hours of exposure. Consider IGIM instead of MMR for infants with household or other prolonged close exposure, because MMR PEP appears less effective in these settings.
- Infants aged 6–11 months who already received an early dose: Consider PEP with IG (within 6 days) or MMR (within 72 hours) on a case-by-case basis; data are insufficient to make a universal recommendation.
- A PEP dose of MMR given at 6–11 months does not count toward the routine series. Two more doses are needed starting at 12 months.
- Do not give MMR and IG at the same time. After IG, wait at least 6 months (IGIM) or 8 months (IGIV) before giving MMR.
6. Reporting
Thank you for your collaboration.
Sincerely,
Ryan Westergaard, MD, PhD, MPH
Chief Medical Officer and State Epidemiologist
Bureau of Communicable Diseases
Division of Public Health
Wisconsin Department of Health Services
Questions
Questions regarding this health alert may be directed to the Bureau of Communicable Disease at dhsdphbcd@dhs.wisconsin.gov.
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