Storage at -3oC for 24 h alters the immunogenicity of pertussis vaccines

Abstract

The immunogenicity of pertussis antigens in an acellular and a whole-cell triple antigen vaccine used for childhoodvimmunisation was assessed in murine models after storage of vaccines below 0°C. Swiss outbred and Balb/c mice received DTPa or DTPw vaccine or placebo. Vaccines were stored at 2–8°C (ideal), or at −3°C for 24 h. Pre and post immunisation IgG responses to pertussis toxin (PT), filamentous haemagglutinin (FHA) and pertactin (PRN) were measured using enzyme immunoassays (EIA). In Balb/c mice, responses to pertactin after receiving adversely stored DTPa were significantly reduced (P=0.005, difference in GMCs 145.9% [24.6–385.4%]). A reduction in GMC to pertactin was also seen in response to adversely stored DTPw (P=0.190, 224.1% [83.8–599.2%]). Outbred mice receiving adversely stored DTPa had lower IgG antibody responses to FHA than those receiving correctly stored vaccine (P=0.002, 522.2% [26.1–2155.6%]). Outbred mice also had a significantly lower response to FHA after administration of DTPw (P=0.009, 14.0% [3.8–51.9%]). Responses to DTPa in both strains generally were greater than those to DTPw. Storage of pertussis vaccines below 0°C appears to alter the immunogenicity of PRN and FHA. Further study is required to determine the effects of such storage on vaccine protective efficacy.