Despite the uptake of ART, HIV-infected children have higher risks of vaccine-preventable disease than HIV-uninfected children (54, 55). Immunological impairment may result from viral replication in lymphoid tissue prior to immunological maturation and the development of protective immune responses (56). In general, infants should be immunised according to local immunisation schedules and ‘non-live’ vaccines should not be delayed (57). However, if ART is indicated for older children with non-protective or absent antibody levels, delaying immunisations until suppression of HIV replication and CD4+ T cells >15% for 6 months should be considered. It should also be noted that the definition of severe immunosuppression by CD4+ T cell count differs according to age in the paediatric population (see table 2).

Table 2: Age-related indicators of severe immunodeficiency in children (56)

Live vaccines in HIV-infected children

 Live vaccines such as MMR and VZV vaccines are a routine component of the childhood immunisation schedule but are contraindicated in severely immunosuppressed children (see table 2). The Bacillus Calmette-Guérin (BCG) vaccine is another live vaccine, contraindicated due to the risk of disseminated BCG infection (58, 59).

MMR is recommended for children who are not severely immunocompromised as per the routine immunisation schedule. It is recommended that VZV-seronegative HIV-infected children should receive 2-dose VZV immunisation (60) and that the doses should be administered at least 2 months apart. Whilst tetravalent MMR-V vaccine is available, the mumps antigen content is higher than the MMR preparation. MMR-V therefore is not recommended due to lack of safety and efficacy data (56). MMR and VZV vaccines may be administered on the same day, or at least 4 weeks apart.

Rotavirus vaccine

 There is significant morbidity and mortality associated with rotavirus infection, although it is unclear whether rotavirus disease is any more severe in HIV infected children (61).  Although the rotavirus vaccine is a live vaccine, there is evidence to suggest that it can be safely administered to infants with HIV who are clinically well (62-64).

 Poliovirus vaccines

 The Inactivated Polio Vaccine (IPV) is administered as a part of the childhood immunisation schedule. There is limited data on the effectiveness of IPV in children with HIV infection, however it is thought that vaccine effectiveness is likely related to immunological status (65). It is recommended that IPV is given as per local immunisation schedules. The oral polio vaccine (OPV) is a live vaccine that is no longer used in Australia.

 Influenza virus vaccine

 Children aged <5 years have a higher risk of hospitalization and morbidity from influenza (66, 67). Influenza vaccine is recommended for all children with HIV infection aged ≥6 months of age. In the first year of administration if the child is less than 9 years of age, 2 doses should be administered 4 weeks apart. The vaccine can be administered as a single dose annually thereafter.

Pneumococcal vaccines

 In addition to the routine childhood immunisation schedule, it is recommended that children with HIV infection receive a dose of PCV13 at 6 months of age and PPV23 at 4 years of age (68, 69).