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Varicella-Specific Immunoglobulin G Titers in Commercial Intravenous Immunoglobulin Preparations


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Intravenous Immunoglobulin Preparations

WHAT’S KNOWN ON THIS SUBJECT: There have been no published reports documenting the efficacy of IVIg in

postexposure prophylaxis since the introduction of an effective vaccine. Although clinicians continue to use this therapy on the basis of experience, there are no objective data on the subject.

WHAT THIS STUDY ADDS: We compared post–vaccine era IVIg products to prevaccine era products, looking at ELISA IgG values as surrogate markers for prophylactic protection. Our finding that postvaccine products are not significantly lower supports the continued use of IVIg for high-risk exposures.


BACKGROUND AND OBJECTIVES: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 nonim-mune, exposed, high-risk patients with varicella-specific immunoglob-ulin. 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 antibod-ies 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.

METHODS: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.

RESULTS: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.

CONCLUSIONS:We found that current IVIg preparations continue to have high levels of varicella-specific IgG despite the changing epidemi-ology 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.Pediatrics2009;124:e484–e488

CONTRIBUTORS:MAJ Ashley M. Maranich, MDa,band

Lt Col Michael Rajnik, MDa

aDepartment of Pediatrics, F. Edward Hebert School of Medicine,

Uniformed Services University of the Health Sciences, Bethesda, Maryland; andbDepartment of Pediatrics, Walter Reed Army

Medical Center, Washington, DC


varicella zoster virus, intravenous immunoglobulin, vaccination


VZV—varicella zoster virus IVIg—intravenous immunoglobulin IgG—immunoglobulin G

ISR—immune status ratio

ELISA— enzyme-linked immunosorbent assay

The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Department of Defense. www.pediatrics.org/cgi/doi/10.1542/peds.2009-0047 doi:10.1542/peds.2009-0047

Accepted for publication Apr 16, 2009

Address correspondence to MAJ Ashley M. Maranich, MD, Walter Reed Army Medical Center, Department of Pediatrics, 6900 Georgia Ave NW, Washington, DC 20307. E-mail: amaranich@ usuhs.mil

PEDIATRICS (ISSN Numbers: Print, 0031-4005; Online, 1098-4275). Copyright © 2009 by the American Academy of Pediatrics


Primary disease with varicella zoster virus (VZV) is responsible for the clini-cal syndrome of chickenpox. Before the widespread use of an effective vac-cine, VZV was a nearly universal child-hood illness in the United States with significant morbidity and mortality. In 1995, the US Food and Drug Adminis-tration licensed a live, attenuated vari-cella vaccine. The following year, a mass immunization campaign for in-fants was initiated in the United States.1 As a result of this campaign,

primary varicella rates in this country have fallen by⬎70%.2

Although vaccination successfully pro-tects against chickenpox and its com-plications, there are certain groups of patients still at risk for this serious disease. In newborns and inadequately protected immunosuppressed patients, exposure to VZV can lead to severe ill-ness with dissemination and even death. Because of this risk, prophylac-tic treatment is recommended after a significant exposure for at-risk, nonim-munized patients in an attempt to pre-vent or attenuate disease.3

Preparations of varicella-specific im-munoglobulin G (IgG) have been used for postexposure passive prophylaxis, having previously been shown effec-tive in preventing or attenuating dis-ease in these clinical situations.4,5

How-ever, the commercial manufacturing of varicella-specific IgG was discontin-ued in 2004 because of declining dis-ease rates. A company in Canada (Can-gene Corporation, Winnipeg, Manitoba, Canada) is currently producing a varicella-specific IgG, but this product has not yet been licensed in the United States. It is available only as an inves-tigational new drug when needed, but this process may be too cumbersome for timely prophylaxis. As a result, phy-sicians are often faced with the need to substitute intravenous immunoglobu-lin (IVIg) treatment in these high-risk

patient groups exposed to or infected with VZV.

There are currently 8 different com-mercially available IVIg preparations that are manufactured from pooled blood product donations of hundreds to thousands of patients. The available IVIg preparations vary with respect to sugar and electrolyte components. Moreover, because each manufac-turer relies on a different pool of do-nors, differences in immunoglobulin content from brand to brand as well as from lot to lot within the same brand are expected.6

As varicella is no longer a common ill-ness, it would be expected that circu-lating antibody levels in the general population have diminished. This is based on decreased primary disease rates as well as the fact that immune individuals are no longer having their immunity regularly boosted by expo-sure to the circulating virus. Because of concerns for waning immunity, the VZV immunization guidelines were re-cently updated to recommend a 2-dose primary vaccination series.7 It is

un-known whether the decreased disease incidence from a successful vaccina-tion program has affected varicella IgG levels in donor-pooled IVIg products.

A study by Audet et al8looked at

mea-sles virus neutralizing antibodies in commercial IVIg preparations. Mea-sles, much like varicella, is a previ-ously endemic viral illness that has largely been eliminated by the use of routine vaccination. This was reflected in their findings of progressively di-minishing antibody levels over the time period of 1999 to 2003. Similar de-cline in antibody levels would be ex-pected for varicella.

There have been no post–vaccine era studies or literature investigating the levels of varicella-specific IgG in IVIg or the effectiveness of IVIg as postexpo-sure prophylaxis in patients at risk. If physicians are to continue to

confi-dently use IVIg for preventing varicella in exposed patients, it is important to determine if this is a valid therapeutic option. The aim of our study was to compare the varicella-specific IgG lev-els in prevaccine and current IVIg products. In addition, we compared the variability of IVIg titers between current IVIg products.


This study was approved by the Walter Reed Army Medical Center institutional review board.


For this study we used historic IVIg samples stored in our research labo-ratory and current IVIg samples from our inpatient hospital pharmacy.

The historic samples were made up of 2 different brands: Gamimune and Sandoglobulin. These preparations date back to the early 1990s, before the introduction of the VZV vaccine. These IVIg lots were retained from previous studies of ␥-globulin preparations and respiratory viruses performed in the 1990s. Since these initial studies, all samples have remained either in lyophilized or premixed form at⫺20°C in monitored freezers in a research laboratory. Samples were thawed and, if necessary, reconstituted per pack-age instructions before testing.

Produced by Bayer Corporation (now Talecris Biotherapeutics, Research Tri-angle Park, NC), Gamimune was the first liquid, ready-to-use IVIg product in the United States. This product is no longer commercially available, having been replaced in 2003 by Gamunex. It was supplied as a ready-to-infuse liq-uid formulation.


Current IVIg samples included all brands currently on formulary at the Walter Reed Army Medical Center in-patient pharmacy: Carimune, Gam-magard, and Gamunex. Gammagard is manufactured by Baxter Health Care (Deerfield, IL) and is also sup-plied in a lyophilized form. Gamunex is the product that replaced Gamimune, a 10% liquid preparation by Talecris Biotherapeutics.

Current IVIg samples were collected over a 6-month period, from August to September of 2008. At the time IVIg was prepared for patient infusion, a vol-ume of pharmacy waste (at least 1 mL) was collected by investigators for study inclusion.

Ten lots of historic samples were tested on the basis of availability: 7 lots of Sandoglobulin and 3 lots of Gamimune. The pharmacy used a total of 24 contemporary IVIg lots during the study period: 10 lots of Carimune, 5 lots of Gammagard, and 9 lots of Gamunex.

Laboratory Testing

All IVIg samples were diluted 1:10 in phosphate-buffered saline before test-ing. Two measurements were obtained from each lot of IVIg.

All samples were tested for varicella IgG levels by using the commercially available varicella-zoster IgG enzyme-linked immunosorbent assay (ELISA) kit by Wampole Laboratories (Cran-bury, NJ), which is routinely used in our serology laboratory. Testing was performed as per the package insert instructions. Assays were automated and performed in batch fashion by us-ing the Grifols Triturus immunoassay analyzer (Grifols USA, Los Angeles, CA) This instrument prepared each plate, read the optical density of each well at 450 nm, and computed final readings. The immune status ratio (ISR) values

were derived from optical density readings by using lot-specific factors provided by the kit manufacturer.

Statistical Analysis

Data were recorded and analyzed by using SPSS software (Chicago, IL). Mean and corresponding SDs were used to summarize varicella titer val-ues. APvalue ofⱕ.05 was considered significant for all comparisons made.


The mean values of each IVIg brand are depicted in Fig 1. The overall average of the historic samples was 3.07 (SD: 0.70), whereas the current samples had a mean of 3.83 (SD: 0.58) (P⫽.01).

There were significant differences be-tween the different brands tested. The average Sandoglobulin ISR values were statistically lower than the Gamimune, Carimune, and Gamunex values (P⬍.01 for all). The Gamunex ISR average was significantly higher than that of the Gammagard lots (P



There has been no study that has defined what level of varicella-specific antibody provides adequate protection in passive prophylaxis usage. Clinical studies have shown varicella-specific immunoglobu-lin to be effective in decreasing the inci-dence and severity of VZV disease in pa-tients at risk.5 The use of IVIg is

supported by a 1984 study by Paryani et al9that compared VZV IgG antibody titers

in immunosuppressed patients after ad-ministration of either varicella-specific immunglobulin or IVIg. Although titers in the varicella-specific immunoglobulin were 18 to 62 times greater than the ti-ters in IVIg, the patient serum assays showed no significant difference in anti-body response between patients treated with varicella-specific IgG and those treated with IVIg, showing that these therapies were equivalent in generating antibody response. Thus, although varicella-specific IgG has been the pro-phylactic treatment of choice, IVIg should provide similar protection.

This is the first study to investigate varicella-specific antibodies in postvac-FIGURE 1


cine products. In this study, current products were not found to contain significantly lower titers of varicella-specific IgG antibody than historic prod-ucts. Thus, the findings of Paryani et al9

remain valid, even in the post–vaccine era, and the continued use of IVIg for pas-sive VZV prophylaxis is justified.

Although we expected to see a decline in the varicella-specific IgG content of post–vaccine era IVIg, this was not the case. This may be attributed to the fact that widespread VZV vaccination in the pediatric population was just started in 1995. The current adult population would not have been a target of this campaign, and the majority of adults would have experienced wild-type varicella disease. The decreased level of circulating virus postvaccine seems to have had minimal effect on antibody levels in IVIg, either be-cause wild-type varicella circulating in the population does not boost immuno-globulin levels or because even a low level of viral circulation provides ade-quate antibody boosting. In 10 to 15 years, the majority of the adult popula-tion will have received VZV vaccinapopula-tion and will not have experienced disease caused by wild-type varicella; repeating this study at that time may show much different results.

It is important to note that all the IVIg products were used as intended for patient infusion. For every brand ex-cept for Gamunex, the products were prepared at a 6% concentration. The ready-to-infuse Gamunex product is supplied as a 10% formulation. Thus, the higher ISR values of this brand may be reflective of this concentration dif-ference. When excluding the Gamunex from sample analysis, the difference

between the historic and current lots is no longer significant.

Our study examined the antibody con-tent of 3 of the 8 commercially avail-able IVIg products. Given that there were, as expected, observed differ-ences in antibody content between the brands studied, one would expect to also see differences between the other brands. Thus, our discussion and con-clusions should be limited to the brands analyzed in this study.

Our study is limited by the inherent dif-ficulties that exist with VZV laboratory testing. The ELISA test that we used is intended for qualitative use, but we used it for quantitative comparisons. Another limitation of this test was seen on initial measurements of undiluted IVIg samples, which exceeded the ca-pacity of the assay. By uniformly dilut-ing the IVIg in phosphate-buffered sa-line, we were able to obtain valid readings used for our analysis. Although there was also concern about the reliability of our assay, we were reassured by the minimal vari-ability among our samples with dupli-cate measurements made on separate days. Because all samples were mea-sured in a single laboratory by using the same ELISA testing kit, it is rea-sonable to draw conclusions on the basis of comparisons of these measurements.

Another limitation of this study is the possibility of loss of protein (immuno-globulin) integrity in the stored IVIg samples. All of these historic lots were well beyond their manufacturer-recommended expiration dates for pa-tient use. However, there are no data regarding the maintenance of protein

levels in these products when stored for long amounts of time. Because all of the prevaccine era IVIg lots had been stored in a⫺20°C freezer, degradation should have been minimal. Nonethe-less, the possibility of antibody degra-dation may explain why the postvac-cine products actually had a higher average ISR value than the prevaccine products.


This is the first study to evaluate the varicella-specific antibody content of IVIg since the introduction of the VZV vaccine in 1995. We found that current IVIg samples do not have lower varicella-specific IgG levels than stored, historic samples. Thus, at this time, physicians can confidently con-tinue to use IVIg as passive prophylaxis for nonimmune, high-risk patients who have been exposed to VZV. Reanalysis of IVIg preparations in 10 to 15 years is warranted, when circulating natural varicella will likely be even lower and when most of the IVIg donor pool will be expected to have vaccine-induced immunity.


We thank Dr Gerald Fisher for supply-ing the historic IVIg samples. We thank the inpatient pharmacy at Walter Reed Army Medical Center and Drs Matthew Eberly, Anjali Kunz, and Dawn Muench for assistance with sample collection. The serology laboratory at Walter Reed Army Medical Center is acknowledged for assistance with sample process-ing. We also thank Cara Olsen for assis-tance with statistical analysis.


1. Centers for Disease Control and Prevention. Prevention of varicella: recommendations of the Advisory Committee on Immunization Practices (ACIP).MMWR Morb Mortal Wkly Rep. 1996;45(RR-11):1–36

2. Seward JF, Watson BM, Peterson CL, et al. Varicella disease after introduction of varicella vaccine in the United States, 1995–2000.JAMA.2002;287(5):606 – 611


4. Brunell PA, Ross A, Miller LH, et al. Prevention of varicella by zoster immune globulin.N Engl J Med.


5. Brunell PA, Gershon AA, Hughes WT, et al. Prevention of varicella in high risk children: a collabora-tive study.Pediatrics.1972;50(5):718 –722

6. Lemm G. Composition and properties of IVIg preparations that affect tolerability and therapeutic efficacy.Neurology.2002;59(12 suppl 6):S28 –S32

7. Marin M, Guris D, Chaves SS, et al. Prevention of varicella: recommendations of the Advisory Committee on Immunization Practices (ACIP).MMWR Recomm Rep.2007;56(RR-4):1– 40 8. Audet S, Virata-Theimer ML, Beeler JA, et al. Measles-virus-neutralizing antibodies in intravenous

immunoglobulins.J Infect Dis.2006;194(6):781–789


DOI: 10.1542/peds.2009-0047 originally published online August 17, 2009;



Ashley M. Maranich and Michael Rajnik

Immunoglobulin Preparations

Varicella-Specific Immunoglobulin G Titers in Commercial Intravenous


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DOI: 10.1542/peds.2009-0047 originally published online August 17, 2009;



Ashley M. Maranich and Michael Rajnik


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by the American Academy of Pediatrics. All rights reserved. Print ISSN: 1073-0397.


FIGURE 1Average ISR values among 5 commercial IVIg preparations.


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