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

The immunogenicity of pertussis antigens in an acellular and a whole-cell triple antigen vaccine used for childhood immunisation was assessed in murine models after storage of vaccines below 0 degreesC. Swiss outbred and Balb/c mice received DTPa or DTPw vaccine or placebo. Vaccines were stored at 2-8 degreesC (ideal), or at - 3 degreesC 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 degreesC appears to alter the immunogenicity of PRN and FHA. Further study is required to determine the effects of such storage on vaccine protective efficacy. (C) 2001 Elsevier Science Ltd. All rights reserved.