Brief Report

Immunogenicity of an Inactivated Hepatitis A Vaccine Maria H. Sjogren, MD, MPH; Charles H. Hoke, MD; Leonard N. Binn, PhD; Kenneth H. Eckels, PhD; Doria R. Dubois, PhD; Lionel Lyde; Amy Tsuchida, MD; Stanley Oaks, Jr., PhD; Ruth Marchwicki, BS; Wayne Lednar, MD, PhD; Robert Chloupek, MD; John Ticehurst, MD; and William H. Bancroft, MD

radioimmunofocus inhibition as previously described (3), and for both total anti-HAV and IgM anti-HAV using commercial radioimmunoassays (HAVAB and HAVAB-M, Abbott Laboratories, North Chicago, Illinois). All serum specimens were tested for alanine aminotransferase (ALT) (normal range, 0.08 to 0.93 /ikat/ L). The Mann-Whitney test was used to compare mean anti-HAV titers in both groups. Confidence intervals and probabilities of observed results were calculated.

Annals of Internal Medicine. 1991;114:470-471. Results Although hepatitis A is a disease without chronic sequelae, it is associated with serious morbidity in adults. An inactivated hepatitis A vaccine prepared at the Walter Reed Army Institute of Research was observed to successfully immunize owl monkeys (1). In a preliminary study, this vaccine was given to eight men, all of whom developed neutralizing antibody to hepatitis A virus (anti-HAV) (2). The present study was designed to confirm the vaccine's immunogenicity, to obtain additional evidence of vaccine safety, and to establish a practical dosing schedule.

The demographic characteristics of both groups were similar. Twenty-one volunteers received four doses and

Methods Forty-two male volunteers, 18 to 50 years of age, were enrolled from among U.S. Army service members serving at Fort Lewis, Washington, D.C. Informed consent was obtained from each volunteer. Volunteers were randomly assigned to receive three doses (0, 1, and 6 months) or four doses (0, 1, 2, and 6 months) of vaccine, 1 mL intramuscularly in the deltoid area. Volunteers recorded local or systemic symptoms occurring within 3 days after each immunization. The vaccine (FI-1/HM175, lot 2) was prepared from human diploid MRC-5 cells infected with HAV strain HM175. The final formulation contained approximately 0.03% of free formalin, 17 ng/mL of hepatitis A antigenic protein, and no adjuvant (2). The vaccine was manufactured at the Biologies Research Department, Walter Reed Army Institute of Research, Washington, D.C. Serologic assays were done before immunization and at monthly intervals thereafter for 8 months. Serum specimens were tested for neutralizing anti-HAV using From Walter Reed Army Institute of Research, Washington, D.C; Fort Lewis, Washington; and United States Army Medical Materiel Development Activity, Frederick, Maryland. For current author addresses, see end of text. 470

Figure 1. Hepatitis A virus neutralizing antibody titer in 42 volunteers immunized with the FM/HM175 vaccine. Serum specimens were tested 8 months after initial immunization. Twenty-one volunteers received vaccine at 0, 1, 2, and 6 months (•), and 21 volunteers received vaccine at 0, 1, and 6 months (O). The mean geometric titer (±SD) was 119 ± 7 for the four-dose group and 103 ± 6 for the three-dose group (P > 0.05).

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21 received three doses. The mean age for the four- and three-dose groups was 33 years and 31 years, respectively. The neutralizing anti-HAV response is shown in Figure 1. At month 8, 36 (86%; 95% confidence intervals, 76% to 96%) of the 42 volunteers (18 in each dose group) had detectable neutralizing antibody. Of these 36, 34 (95%) had a titer of at least 1:40 and 2 (5%) had a titer of 1:10. The geometric mean titer was similar in both groups (118.9 compared with 103.3, P > 0.05). The observed 86% immunogenicity rate exceeded the 70% rate that had been defined in advance as the acceptable immunization rate. Using a commercial radioimmunoassay, HAVAB, we detected total anti-HAV (>50% inhibition) in 10 of 21 (48%) volunteers who received four vaccine doses and in 7 of 21 (33%) volunteers who received three doses (P > 0.05). We did not detect IgM anti-HAV in any serum specimen. Of those reporting pain at the site of inoculation on their questionnaires, 97% described the pain as mild to moderate (average duration, 20 minutes). No systemic side effects were observed. Five volunteers had minimal ALT abnormalities (range, 0.95 to 1.35 /xkat/L). These subjects were asymptomatic and their ALT levels subsequently returned to normal. Serum samples from these subjects did not show the presence of IgM antiHAV. Discussion Hepatitis A accounts for 44.2% of the cases of clinical hepatitis reported to the Centers for Disease Control (4). Because of the growing proportion of seronegative persons in the United States, especially among adults who are most likely to experience clinical hepatitis A, HAV remains an epidemic threat in the United States, as well as in other industrialized countries. We have shown that the FI-1/HM175 vaccine was immunogenic in 86% of the subjects and that three doses were as immunogenic as four. The vaccine was found to be safe and acceptable for use in healthy adults. That most subjects had neutralizing anti-HAV titers of at least 1:40 suggests that the vaccine performs better than immune serum globulin, which has been reported to generate a peak neutralizing antibody titer of 1:40 or less (5).

That more serum specimens were not positive for anti-HAV by the HAVAB test is not surprising. The test was designed to detect higher concentrations of naturally acquired antibody. Hepatitis A vaccine induces a lower anti-HAV response; therefore, the test may not be adequate to detect low serum levels of anti-HAV. The three-dose schedule (0, 1, and 6 months) used in our study is similar to the accepted hepatitis B immunization program, which could prove to be advantageous for future combined hepatitis A and B vaccine programs. The opinions contained herein are those of the authors and should not be construed as representing those of the Department of the Army or Department of Defense. Acknowledgments: The authors thank Sergeant Richard Lewis and Major Keith Shafer for assistance in conducting the study and Robert Burge for statistical analysis. Requests for Reprints: Maria H. Sjogren, MD, MPH, Department of Virus Diseases, Walter Reed Army Institute of Research, Washington, D.C. 20307-5100. Current Author Addresses: Drs. Sjogren, Hoke, Binn, Eckels, Dubois, and Ticehurst, Mr. Lyde, and Ms. Marchwicki: Walter Reed Army Institute of Research, Washington, D.C. 20307-5100. Dr. Tsuchida: Department of Gastroenterology, Fort Lewis, WA 98433. Dr. Oaks: Institute of Medicine, National Academy of Sciences, 2101 Constitution Avenue, NW, Washington, D.C. 20418. Dr. Lednar: Building 320, Eastman-Kodak, Kodak Park Company, Rochester, NY 14652-3615. Dr. Chloupek: HQ, Forces Command (FCMD), Fort McPherson, GA 30330-6000. Dr. Bancroft: HQ, VSAMRDC, SGRD-PLA, Fort Detrick, Frederick, MD 21702-5012. References 1. Binn LN, Bancroft WH, Eckels KH, et al. Inactivated hepatitis A virus vaccine produced in human diploid MRC-5 cells. In: Zuckerman AJ, ed. Viral Hepatitis and Liver Disease. New York: Alan R. Liss, Inc; 1988:91-3. 2. Sjogren MH, Eckels KH, Binn LN, et al. Safety and immunogenicity of an inactivated hepatitis A vaccine. In Zuckerman AJ, ed. Viral Hepatitis and Liver Disease. New York: Alan R. Liss, Inc; 1988: 94-6. 3. Lemon SM, Binn LM. Serum neutralizing antibody response to hepatitis A virus. J Infect Dis. 1983;148:1033-9. 4. Hepatitis Surveillance Report No. 52. Atlanta, Georgia: Centers for Disease Control; 1989:10. 5. Stapleton JT, Jansen R, Lemon SM. Neutralizing antibody to hepatitis A virus in immune serum globulin and in the sera of human recipients of immune serum globulin. Gastroenterology. 1985;89:63742.

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• Volume 114 • Number 6


Immunogenicity of an inactivated hepatitis A vaccine.

Brief Report Immunogenicity of an Inactivated Hepatitis A Vaccine Maria H. Sjogren, MD, MPH; Charles H. Hoke, MD; Leonard N. Binn, PhD; Kenneth H. Ec...
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