From the Guidelines
Measles virus shedding after measles vaccination is not a significant concern, as the vaccine strain virus is weakened and shedding is minimal, with no transmission risk to others, according to the 2013 IDSA clinical practice guideline for vaccination of the immunocompromised host 1.
The measles vaccine contains a live attenuated virus that replicates at low levels in the body to generate immunity. However, the shedding of the measles virus is not mentioned as a concern in the provided evidence, with the table indicating "Measles: no" shedding of the agent, suggesting that measles virus shedding is not a significant risk after vaccination 1.
Key points to consider:
- The vaccine strain virus is significantly weakened compared to wild measles, reducing the risk of transmission.
- The replication of the vaccine virus is necessary to stimulate a robust immune response but is controlled enough that it doesn't cause disease in the vaccinated person or pose substantial risk to others.
- As a precaution, recently vaccinated individuals should practice good hygiene and may want to limit close contact with severely immunocompromised people during the period after vaccination, although the specific duration of shedding is not provided in the evidence.
- The period of viral replication and development of immunologic response after live viral vaccines is generally <3 weeks, so vaccination ≥4 weeks prior to immunosuppression is likely to be safe 1.
From the Research
Measles Virus Shedding After Vaccination
- The duration of measles virus shedding after measles vaccination is not explicitly stated in most of the provided studies 2, 3, 4, 5.
- However, one study found that shedding of measles vaccine RNA can be detected up to 29 days post MMR vaccination, with a median interval of 11 days after the first dose and 18.9 days after the second dose 6.
- The amount of vaccine RNA shedding is indicated to be low, as shown by high cycle threshold (Ct) values, with a median Ct value significantly higher than that in children with wild-type infection 6.
- It is recommended that clinicians and public health officials consider performing measles vaccine testing on those testing positive for measles within one month of MMR vaccination, especially if the Ct value is high and definitive epidemiological links are absent 6.