We have a 40 lb six-year-old patient who has been taking 15 mg of methotrexate weekly for arthritis for 12 months. Can we give the child MMR and varicella vaccine based on this methotrexate dosage?

Based on the weight and dosage provided (40 lbs and 15 mg/week), the child is currently receiving more than 0.4 mg/kg/week of methotrexate. This meets the Infectious Disease Society of America (IDSA) definition of high-level immunosuppression. Administration of both varicella and MMR vaccines are contraindicated until such time as the methotrexate dosage can be reduced. The 2013 IDSA definition of low-level immunosuppression for methotrexate is a dosage of less than 0.4 mg/kg/week. For additional details, see the 2013 IDSA Clinical Practice Guideline for Vaccination of the Immunocompromised Host: cid.oxfordjournals.org/content/early/2013/11/26/cid.cit684.full.pdf.

As a general rule, whenever feasible, it is recommended that non-live and live vaccines be administered 2 or more weeks before initiating immunosuppressive medications include human immune mediators like interleukins and colony-stimulating factors, immune modulators, and medicines like tumor necrosis factor-alpha inhibitors and anti-B cell agents. See CDC General Best Practice Guidelines for Immunization section on altered immunocompetence: www.cdc.gov/vaccines/hcp/acip-recs/general-recs/immunocompetence.html.