Varicella-specific immunoglobulin G titers in commercial intravenous immunoglobulin preparations

Since the introduction of an effective vaccine in 1995, the incidence of primary varicella zoster virus (VZV) has greatly decreased. However, newborns and immunocompromised patients remain at risk for serious disease. Currently, varicella-specific immunoglobulin is recommended for treatment of nonimmune, exposed, high-risk patients with varicella-specific immunoglobulin. However, product inavailability has led to substitution of intravenous immunoglobulin (IVIg) for such prophylaxis on the basis of studies from the preimmunization era. No studies in the post-vaccine era have shown that IVIg contains adequate varicella-specific antibodies to protect patients at high risk. The overall effect of vaccination on varicella-specific immunoglobulin G (IgG) levels in donor-pooled IVIg products is unknown. We compared the varicella-specific IgG levels in prevaccine and current IVIg products.

We used stored historic IVIg samples and current samples from our inpatient pharmacy. All samples were tested for varicella-specific IgG levels by enzyme-linked immunosorbent assay.

Ten historic lots and 24 current lots were tested. The overall mean value of varicella-specific IgG in the historic lots was 3.07 (SD: 0.70); the current lots had a mean of 3.83 (SD: 0.58). The postvaccine IVIg contained higher levels of antibody than the prevaccine lots.

We found that current IVIg preparations continue to have high levels of varicella-specific IgG despite the changing epidemiology of how immunity has been obtained. Given the results of this study, it is reasonable for physicians to comfortably substitute IVIg for varicella-specific immunoglobulin preparations when treating high-risk patients exposed to VZV.