CDC guidance for public health authorities on use of a 3rd dose of MMR vaccine during mumps outbreaks

During its October 2017 meeting, the Advisory Committee on Immunization Practices (ACIP) recommended a third dose of a MMR vaccine* for groups of people who public health authorities determine are at increased risk for acquiring mumps because of an outbreak. Based on that recommendation, when mumps outbreaks occur, public health authorities should be prepared to do the following:

  • identify groups of people who may have close contact with a mumps patient during an outbreak
  • investigate the setting to determine if a group is at increased risk for acquiring mumps and should receive a third dose of MMR vaccine

The purpose of the following guidance is to help health authorities determine when to recommend a third dose of MMR vaccine during an outbreak of mumps.

Identify groups who may have close contact with a mumps patient

Public health authorities should first identify groups of people who have or likely have close contact with a mumps patient.

Close contact is defined as:

  1. having direct contact with a mumps patient’s infectious respiratory secretions by droplet transmission (e.g., kissing, sharing saliva-contaminated objects like water bottles, or being coughed or sneezed on). Droplets generally travel ≤3 feet when an infected person talks, coughs, or sneezes; or
  2. being in close proximity for a prolonged period of time with a person infected with mumps during their infectious period (2 days prior, to 5 days after, onset of parotitis or other salivary gland swelling)

Public health authorities should focus efforts to identify groups of people who are likely to have close contact with a mumps patient, and not just a mumps patient’s immediate close contacts (i.e., groups known to have close contact, like family members, partners, or roommates). Examples of groups with likely close contact include:

  • students from the same study group, social group, fraternity, or sorority as a mumps patient
  • coworkers on the same shift or who socialize after work with a mumps patient
  • athletes who share sports facilities or equipment with a mumps patient

If you determine that a group is at increased risk (see next section), it is important to vaccinate groups of people who are likely to have close contact, in addition to those with known close contact, to maximize the number of people who would benefit from a third dose (i.e., persons not already infected). The vaccine has not been shown to be effective at preventing disease in people already infected with mumps virus (i.e., post-exposure mumps vaccination is not recommended).

Assess Transmission in the Outbreak Setting to Determine Increased Risk

After identifying groups of people who have or likely have close contact with a mumps patient, public health authorities should then investigate the setting where exposures are occurring. A group’s setting could be at a location such as a church or school, during an activity such as sports practice, or at an event such as a party.

Two main questions about a group’s setting can guide a health department when determining if a group is at increased risk:

  1. Is there evidence that transmission occurred or has continued to occur within the group’s setting (i.e., did mumps patient(s) acquire mumps from close contact exposures within a setting as opposed to outside the setting)?
  2. Is there likely to be intense or frequent transmission in the group’s setting (i.e., are behaviors among persons in the group likely to result in continued or wide-spread transmission)?

Public health authorities can use their answers to these questions in a decision matrix to determine if the group is at increased risk for acquiring mumps (Table 1) and should receive a 3rd MMR dose, as stated in the ACIP recommendation. Criteria for classifying evidence of transmission and likelihood of transmission to use in the matrix are detailed in the next sections.

Table 1. Decision matrix to assist public health authorities when determining if a group of people is at increased risk for acquiring mumps during an outbreak

Table 1. Decision matrix to assist public health authorities when determining if a group of people is at increased risk for acquiring mumps during an outbreak
Evidence of transmission in the setting Likelihood of transmission in the setting
Low Moderate High
No evidence of transmission Not at increased risk Not at increased risk Might be at increased risk
Evidence that transmission occurred Not at increased risk Might be at increased risk At increased risk
Evidence of sustained or extensive transmission Might be at increased risk At increased risk At increased risk

How to determine if there is evidence of transmission in the setting

You can determine the evidence of transmission for mumps in a setting by looking at the number of incubation periods (average 16–18 days) since the first patient’s onset of parotitis (or other salivary gland swelling), or you can also do this by looking at epidemiological links among cases. Evidence of transmission is classified as follows (Table 2):

Table 2. Classification of evidence of transmission in a setting based on incubation period(s) since first case onset or epidemiological links among cases during a mumps outbreak

Table 2. Classification of evidence of transmission in a setting based on incubation period(s) since first case onset or epidemiological links among cases during a mumps outbreak
Evidence of transmission Incubation period(s) since parotitis onset of first case Epidemiological link
No evidence of transmission Case onsets <1 incubation period OR Case(s) likely exposed outside the setting (e.g., linked to an external event or other outbreak, associated with travel)
Evidence that transmission occurred Case onsets 1 to <2 incubation periods OR Case(s) likely exposed within the setting and close contact with a primary case(s) was reported (e.g., socialized or attended the same party with a patient)
Evidence of sustained or extensive transmission Case onsets ≥2 incubation periods OR Case(s) likely exposed within the setting, close contact exposures are difficult to identify, and there is an increasing number of cases (e.g., cannot be epidemiologically linked to a known case or are linked to multiple cases)

How to determine if there is likelihood of transmission in the setting

Likelihood of transmission in the setting depends on close contact behaviors among people in a group and increases with:

  • intensity of close contact exposures (e.g., physical contact, such as attendance at a crowded party, or during dancing, contact sports, kissing or sexual activity; sharing of gym equipment or drinks)
  • frequency of close contact exposures (e.g., prolonged contact such as living in confined or shared spaces; repeated contact such as meeting regularly or sharing daily habits)

Public health authorities will have to assess these behaviors for their likelihood of transmission for each group, as they can vary widely across settings and between outbreaks. In Table 3, we provide examples of settings considered to have low, moderate, and high likelihood of transmission.

Table 3. Examples of settings with low, moderate, and high likelihood of transmission during a mumps outbreak

Table 3. Examples of settings with low, moderate, and high likelihood of transmission during a mumps outbreak
Likelihood of transmission in the setting Community University or college campus School (K–12) Work place (office building)
Low Community festival or fair with infrequent social interaction* among attendees Lecture halls, dorms with infrequent social interaction* Classrooms without cases Building floor with shared break room
Moderate Church group; hobbyist group with frequent meetings; choir Social group, house/dorm with moderate social interaction*; non-sport extracurricular groups Classrooms with cases; afterschool activities other than sports Project group that meets daily
High Large close-knit community, household, or social group; gym with regular close contact among members; crowded venues such as clubs or bars House/dorm with intense social interaction*; fraternities/sororities; sports teams Gym class or other class involving close contact activities; adolescent friend group; sports teams Group of employees who regularly socialize

*Social interaction includes attending parties or other social gatherings together, sharing drinks, dancing, or playing sports.

Additional factors to consider beyond evaluating transmission in the setting

The following factors are outside the criteria defined in the tables above but also may guide public health authorities when determining if a group is at increased risk and should receive a third dose of MMR vaccine during an outbreak:

Public health authorities may be more likely to recommend a third MMR dose for

  • A small, defined target group
  • A large population with intense close contact
  • When the case count is rapidly increasing, i.e., a steep upslope in the epi-curve
  • When the group at increased risk for acquiring mumps includes persons who might potentially transmit to a susceptible population, e.g., students who work or volunteer in hospitals or child care centers
  • The setting is known to be high risk for transmission based on previously reported outbreaks, e.g., fraternities, sports teams, or close-knit communities

Public health authorities may be less likely to recommend a third MMR dose for

  • A group that has few mumps cases that are dispersed in a large population
  • A setting where close contact exposures are unclear or unlikely to occur again
  • When the case count remains low over multiple incubation periods
  • When the number of cases is declining

Factors to Consider When Implementing a Third Dose Recommendation

Everyone who is determined to be part of the group at increased risk for getting mumps should receive a dose of MMR vaccine. That includes people who do not have vaccine records that prove they received two doses of MMR vaccine in the past, and people who have evidence of presumptive immunity other than documented two doses of MMR vaccine. No additional dose is recommended for people who already received three or more doses before the outbreak.

Public health authorities should work with healthcare providers and institutions to notify people that they are at increased risk and should receive a dose of MMR vaccine. Remember to tell these people:

  • You should try to get MMR vaccine through routine channels, like from your healthcare provider. (Or if the health department opts to provide vaccine, through designated vaccine clinics).
  • MMR vaccine is not 100% effective, so there is a chance you could still get mumps even if you get vaccinated.
  • MMR vaccine will not prevent you from getting mumps if you are already infected with the virus. It usually takes 16 to 18 days for mumps symptoms to show up after you are infected. So if you were exposed, it is possible that you are already infected but do not yet have symptoms.
  • The most common mumps symptoms include fever, headache, muscle aches, tiredness, loss of appetite, and puffy cheeks caused by swollen/tender salivary glands under the ears on one or both sides (parotitis).
  • If you have mumps, you should avoid contact with other people until at least 5 days after you start to have puffy cheeks (swollen salivary glands).

When to Further Expand the Public Health Response

Public health authorities may choose to expand their response if they determine additional action is necessary.

You might consider an expanded public health response when, for example:

  • case counts are increasing despite a recommendation for third dose administration to a small, defined group
  • there is poor vaccine access or low vaccine uptake among the group(s) at increased risk for acquiring mumps
  • the group(s) at increased risk includes hard-to-reach or vulnerable populations

Expanded responses could include:

  • broadening recommendations for 3rd dose vaccination to all persons in the larger outbreak setting (e.g., institution-wide or community-wide)
  • coordinating vaccine supply or setting up special vaccination clinics
  • escalating outreach efforts
  • promoting an organized vaccination campaign

During an expanded response, you may opt to recommend a dose of MMR vaccine for all people at increased risk without verifying their vaccination history. The purpose of this would be to avoid delays caused by having to review individual records. You can tell people who received a dose during the outbreak to talk to their health care provider so the provider can assess the need for additional doses to ensure age-appropriate vaccination.

*The third dose may be administered as measles, mumps, rubella (MMR) vaccine for persons ≥12 months of age, or measles, mumps, rubella, and varicella (MMRV) vaccine for children aged 1–12 years. This document references the use of MMR vaccine as the third dose, as this would be the most likely mumps virus-containing vaccine administered during an outbreak. Additionally, previous doses of MMRV vaccine should be considered when assessing number of mumps vaccine doses received prior to an outbreak.