Some pregnancies are closely spaced. Should we give Tdap during each pregnancy, even if it means mothers would get 2 doses within 12 months?

Yes. ACIP looked into this issue and included related information in its recommendations published in MMWR on February 22, 2013 (www.cdc.gov/mmwr/preview/mmwrhtml/mm6207a4.htm). ACIP reviewed available data on birth statistics and found that among those in the U.S. who have more than one pregnancy, a very small percentage (2.5%) have an interval of 12 months or less between births. The majority of people who have two pregnancies have an interval of 13 months or more between births. Approximately 5% of mothers have four or more pregnancies. ACIP concluded that (1) the interval between subsequent pregnancies is likely to be longer than is the persistence of maternal anti-pertussis antibodies, (2) most mothers would receive only 2 doses of Tdap, and (3) a small proportion of mothers would receive 4 or more doses.

A theoretical risk exists for severe local reactions (e.g., Arthus reactions, whole limb swelling) for pregnant people who have multiple, closely spaced pregnancies. However, the frequency of side effects depends on the vaccine’s antigen content and product formulation, as well as on preexisting maternal antibody levels related to the interval since the last dose and the number of doses received. The risk for severe adverse events has likely been reduced with current vaccine formulations (including Tdap), which contain lower doses of tetanus toxoid than did older vaccine formulations. ACIP believes the potential benefit of preventing pertussis morbidity and mortality in infants outweighs the theoretical concerns of possible severe adverse events in mothers.