Authors: Shahana A. Choudhury.
Introduction: Minimal data exists regarding prevalence of immunity to inactivated poliovirus vaccine (IPV) in previously vaccinated HIV-infected children.
Methods: Antibody titers to IPV against serotypes (ST) 1, 2 and 3 following 3-doses (primary series) and 4th and 5th doses (booster) were examined in 59 children who were born to HIV-infected mothers. Eight of those children tested negative for HIV by DNA PCR and served as the controls for the 3rd and 4th dose recipients. Anti-polio 1, 2, 3 antibody titers (1/dil) was measured by neutralization assay at Specialty Laboratory in New Jersey. Correlate of protective immunity (PI) was defined as antibody titer >1:8 for all serotypes. ST specific PI was correlated with the T cell counts and clinical disease categories within the HIV-infected children. PI status was compared between the HIV- infected and HIV- uninfected children and between the numbers of vaccine dose recipients within the HIV-infected children.
Results: Mean age of children at the time of vaccination was 6.6, 18.6 and 66.5 months in the 3rd, 4th and 5th dose recipients, respectively. The mean age of the HIV-infected and HIV- uninfected children was comparable in the 3-dose group. Among the 3rd and 4th dose recipients, prevalence of PI to all 3 ST was significantly (p= 0.002/ST1, 0.002/ST2 and 0.01/ST3) lower in the HIV-infected, compared to their uninfected counterparts; Within the HIVinfected children, prevalence of PI to ST 1 and 2 was around 7-10 percent for all dose recipients; and 28 percent to ST3 for the 5th dose vaccine recipients. The CD4 count was found to be significantly (p=0.009) lower (362/mm3) in the 5th dose compared to the 3rd dose vaccine recipients (1072 /mm3).
Conclusion: A significantly high proportion of HIV- infected children may remain unprotected against all ST of IPV even after their booster doses and thus may remain at risk for infection with all 3 ST of poliovirus when exposed to recipients of the live oral polio vaccine worldwide. Global implementation of IPV over OPV may be considered to prevent resurgence of poliovirus disease in the growing population of immunocompromised patients. Extra vigilance in the maintenance of protective immunity to poliovirus serotypes and surveillance of disease in the immunocompromised host may be deemed necessary for prevention of disease occurrence and timely diagnosis and treatment.
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