Similar vaccines made by different manufacturers can differ in the number and amount of their specific antigenic components and formulation of adjuvants and conjugating agents, thereby eliciting different degrees of immune response. However, such vaccines have been considered interchangeable by most experts when administered according to their licensed indications, although data documenting the effects of interchangeability are limited. Licensed vaccines that may be used interchangeably during a vaccine series from different manufacturers, according to recommendations from the ACIP or AAP, include diphtheria and tetanus toxoids vaccines, hepatitis A vaccines, hepatitis B (HepB) vaccines for infants, and rabies vaccines (see Rabies). An example of similar vaccines used in different schedules that are not recommended as interchangeable is the 2-dose HepB vaccine option currently available for adolescents 11 through 15 years of age. Adolescent patients begun on a 3-dose HepB regimen are not candidates to complete their series with HepB vaccine used in the 2-dose protocol, and vice versa, and the 2-dose schedule is applicable only to Recombivax HB (see Hepatitis B).

Licensed Hib conjugate vaccines are considered interchangeable for primary as well as for booster immunization as long as recommendations concerning conversion from a 3-dose regimen (PRP-OMP) to a 4-dose regimen (all other conjugated PRP preparations) are followed (see Haemophilus influenzae Infections). Licensed rotavirus (RV) vaccines are considered interchangeable as long as recommendations concerning conversion from a 2-dose regimen (RV1) to a 3-dose regimen (RV5) are followed (see Rotavirus).

Minimal data on safety and immunogenicity and no data on efficacy are available for different DTaP vaccines when administered interchangeably (see Pertussis). However, in circumstances in which the type of DTaP product(s) received previously is not known or the previously administered product(s) is not readily available, any of the DTaP vaccines may be used according to licensure for dose and age. Matching of adolescent Tdap manufacturer with pediatric DTaP manufacturer is not necessary. For interchangeability of combination vaccines, including DTaP-HepB-IPV and DTaP-IPV/Hib combination vaccines, see Combination Vaccines . These recommendations may change as additional data become available.