Krause PR, Klinman DM. Varicella vaccination: evidence for frequent reactivation of the vaccine strain in healthy children.
Nat Med 2000;
6:451-4. [PMID:
10742154 DOI:
10.1038/74715]
[Citation(s) in RCA: 78] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Wild-type varicella zoster virus (VZV) causes chickenpox, a common childhood illness characterized by fever and a vesicular rash and rare serious complications. Wild-type VZV persists in a latent form in the sensory ganglia, and can re-activate to cause herpes zoster. More than 10 million American children have received the live attenuated Oka strain VZV vaccine (OkaVZV) since its licensure in 1995. Pre-licensure clinical studies showed that mean serum anti-VZV levels among vaccinees continued to increase with time after vaccination. This was attributed to immunologic boosting caused by exposure to wild-type VZV in the community. Here, we examine the alternative, that large-scale asymptomatic reactivation of OkaVZV might occur in vaccinees. We analyzed serum antibody levels and infection rates for 4 years of follow-up in 4,631 children immunized with OkaVZV. Anti-VZV titers decreased over time in high-responder subjects, but rose in vaccinees with low titers. Among subjects with low anti-VZV titers, the frequency of clinical infection and immunological boosting substantially exceeded the 13%-per-year rate of exposure to wild-type varicella. These findings indicate that OkaVZV persisted in vivo and reactivated as serum antibody titers decreased after vaccination. This has salient consequences for individuals immunized with OkaVZV.
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