Comparison of a recombinant DNA hepatitis B vaccine alone or in combination with hepatitis B immune globulin for the prevention of perinatal acquisition of hepatitis B carriage Y. Poovorawan, S. Sanpavat, W. Pongpunlert, S. Chumdermpadetsuk, P. Sentrakul*, S. Chitinand, R. Sakuiramrung t and ¥. Tannirundorn* The protective efficacy of a recombinant DNA yeast-derived hepatitis B vaccine was assessed alone or in combination with hepatitis B immune globulin (HBIg) in neonates born to surface antigen ( HBsAg)-positive and e antigen (HBeAg)-positive mothers. Neonates received either a 10/tg dose of vaccine alone or the same dose of vaccine plus 0.Sml HBIg within 12 h of birth. All infants subsequently received 10 I~g of vaccine at 1, 2 and 12 months. Only two of the 58 (3.4~ ) newborns of HBsAg-positive/HBeAg-positive mothers receiving vaccine alone became chronically infected with hepatitis B virus (HBV) while all infants administered vaccine + HBIg were protected. These results indicate that although the administration of HBIg can increase the protection rate, the use of vaccine without concomitant administration of HBIg according to the above schedule could considerably reduce the risk of perinatal HB V transmission.

Keywords:HepatitisB; recombinantvaccine;hepatitisBimmuneglobulin;carrierstate;neonates;antibodypersislence Introduction Hepatitis B infection constitutes a major and growing world-wide public health problem. The prevalence of this disease is especially high in parts of Southeast Asia where hepatitis B virus (HBV) transmission at or near the time of birth accounts for an inordinately high proportion of infected infants ~. As many as 65-90% of infants born to HBV-carrier mothers who are positive for hepatitis B surface (HBsAg) and e (HBeAg) antigens go on to become chronic carriers 2-7. In addition to serving as a continuous reservoir for HBV transmission, a large proportion of this population will develop hepatitis B-related diseases later in life including chronic hepatitis, liver cirrhosis and primary hepatocellular carcinoma a'9. Therefore, it is essential that perinatal HBV infection be prevented. While numerous studies in Asia have established that hepatitis B immune globulin (HBIg) alone or in combination with hepatitis B vaccines can significantly prevent perinatal acquisition of HBV carriage s-7'1°-~3, the large-scale use of HBIg is prohibitive due to high cost, limited availability and logistical considerations. Immunoprophylaxis by the sole use of hepatitis B vaccine would therefore be a more cost-effective way of controlling the incidence of vertically transmitted chronic HBV carriage. The results of a recent study carried out in Thailand using a recombinant yeast-derived hepatitis B vaccine demonstrated the feasibility of such an approach ~4. Infants of women who were HBsAg-positive and HBeAg-positive (s + / e + ) received a 10~g dose of the vaccine within 12 h of birth followed by administration Department of Pediatrics, Obstetrics and Gynaecology*, Microbiology ~, Faculty of Medicine, Chulalongkorn University and Hospital, Bangkok, Thailand 0264-4IOX/90/S10056-04 .(: 1990 Butterworth & Co. (Publishers) Ltd $56

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of similar doses i, 2 and 12 months later. Only two (3.6%) of the 55 infants who were followed up for 13 months became chronically infected. In parallel, a second group of neonates was also vaccinated with the yeastderived vaccine following a similar schedule, but 0.5 ml HBIg was administered with the first vaccine dose. Preliminary results in this second group of infants are now available and permit a comparison of the protective efficacy of the vaccine along with that of vaccine + HBIg in newborns at risk of perinatal acquisition of hepatitis B carriage.

Materials and methods A total of 6407 pregnant women attending the maternity clinic at Chulalongkorn Hospital (Bangkok, Thailand) were systematically screened (at month 6 or 7 of pregnancy) for the presence of HBsAg using an enzymelinked immunosorbent assay, radioimmunoassay (RIA) or reverse passive haemagglutination. Detection of HBeAg was performed by RIA at the Catholic University of Louvain, Belgium. Healthy neonates to those mothers found to be s t / c -~ were eligible for inclusion in these trials. Infants were given either a 10 #g dose of a yeast-derived hepatitis B vaccine (study A) or the hepatitis B vaccine + 0.5 ml HBIg within 12 g of birth (study B). Injections were administered i.m. in the anterolateral thigh or the deltoid region. All infants subsequently received 10#g of recombinant vaccine at months 1, 2 and 12. Infants born to mothers whose serological status was either HBsAg-positive/ HBeAg-negative (s + / e - ; n = 97) or HBsAg-negative/ HBeAg-negative ( s - / e - ; n=56) were also inoculated with hepatitis B vaccine as part of study A.

Protective efficacy of hepatitis B vaccine in neonates: Y. Poovorawan et al. I00" 90" 80"

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Figure I Seroconversion rates in infants receiving 10/Jg of yeastderived hepatitis B vaccine at months 0, 1, 2 and 12 according to their mothers' serological status: IB, s + / e + mothers; [ ] , s + / e - - mothers; I-7, s-- mothers

Venous blood samples were drawn prior to each injection (months 0, 1, 2 12) as well as at months 4, 9, and 13 to determine carrier status as well as the level of antibody to HBsAg (anti-HBs). The recombinant yeastderived hepatitis B vaccine (Engerix-B) was developed by SmithKline Biologicals (Rixensart, Belgium). HBsAg polypeptides in this vaccine, expressed in Saccharomyces cerevisiae, have been shown to have immunological properties analogous to those of plasma-derived vaccines 15-17. Extensive clinical testing have proven that the vaccine is safe and immunogenic in adults and children 18. Commercially available kits (Auzyme II, Ausria II, Abbott Laboratories, Chicago, IL, USA) were used to test for the presence of HBsAg and HBeAg. Anti-HBs levels (Ausab, Abbott) were expressed in international units. Seroconversion was defined as antibody titres /> 1 mIU ml-1 in serum samples from infants originally below the detection limit of the RIA ( < 1 mIU ml- 1). In cases where infants were given HBIg, vaccine-induced antibodies were measured from month 4 onwards, as exogenous immunoglobulin titres become negligible by this time.

month 13. In study B, 48 infants have thus far been followed up for 9 months. Vaccine safety and reactogenicity were assessed for 3 days following vaccination. No serious adverse effects were reported after any vaccine dose in either study. The few local and general-reactions Observed were all mild and transient. In study A, the seroconversion rates and geometric mean titres (GMTs) of neonates of s +/e + mothers were compared with those of neonates of mothers who were s + / e - and s - / e - . As seen in Figure 1, there appeared to be no difference between the seroconversion rates of these three groups of infants. One month after the first dose, ~25% of all vaccinees seroconverted, while an average of 93 % had seroconverted by month 2. At month 4, virtually all infants showed measurable anti-HBs titres. Figure 2 shows the corresponding GMTs for these neonates. No significant differences emerged between the three groups: overall GMTs rose from 4mIUm1-1 at month 1, to 13, 209, 246 and 138mIUm1-1 at months 2, 4, 9 and 12, respectively (Table I). By month 13, the booster dose increased the overall GMT by > 20-fold. At month 4, 95% of all vaccinees had titrcs > 10mIU ml- 1, while 70% showed anti-HBs levels > 100mIU ml- 1. One month after the booster dose of vaccine (month 13), 96.4% (163/169) of all infants had antibody titres > 100 mlU ml- t. As seen in Table I, the concurrent administration of HBIg did not interfere with the anti-HBs response in

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After screening pregnant women for hepatitis B markers, 68 and 78 neonates born to s + / e + mothers were enrolled in studies A and B, respectively. A total of 58 out of 68 newborns in study A were available for follow-up at

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Tellde 1 Serological results in neonates vaccinated with 10#g of hepatitis B vaccine alone (maternal marker status: s + / e + , s + / e - , or with 10gg hepatitis B vaccine +0.5ml HBIg (infants of s + / e + mothem only)

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Seroconversion rate Seroconversion (%) GMT

64/64 100 185

46/47 98 230

26/26 100 159

13/13 100 5554

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newborns to the recombinant hepatitis B vaccine. There are no significant differences in the seroconversion rates or G M T s between the two groups. The protective efficacy of the vaccine administered alone or with HBIg for neonates of s + / e + mothers is shown in Figures 3 and 4, respectively. Serum samples obtained from the infants in both studies were tested at various months for the presence of HBsAg. In study A, four newborns were initially found to be positive for the antigen. Subsequent samples from three of these newborns indicated that the antigenaemia observed initially might possibly have been due to low-level contamination in utero or at birth, but did not result in persistent infection. Only two of the 58 infants (3.4%) followed from birth to 13 months become chronically infected with HBV as shown by the persistent presence of HBsAg in their serum samples. One of these infants was HBsAg-positive from birth, the other from month I onwards. Neither child developed anti-HBs in the course of the 13 month follow-up period. In study B (Figure 4), five of the 48 infants followed up for 9 months were initially positive for HBsAg: none became chronically infected. Therefore, these infants show a chronic carrier rate of < t/48 or 2.1%. Discussion

Infants born to mothers who are chronic HBsAg carriers, especially mothers who are also positive for HBeAg, are at very high risk of becoming chronically infected carriers themselves. The results of our studies indicate that early vaccination with a recombinant yeast-derived hepatitis B vaccine can, by itself, considerably reduce the frequency of chronic HBs-antigenaemia resulting from

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et al.

perinatal HBV transmission. Fifty-six out of 58 high-risk infants, inoculated with 10 pg of the recombinant vaccine at 0, 1, 2 and 12 months, produced elevated anti-HBs titres, which will probably provide them with adequate protection against HBV infection for several years. Only two of these neonates (3.4%) have developed chronic hepatitis B infection. One of these newborns had most probably been infected in utero, while the other acquired the virus soon after birth. If further studies involving larger numbers of neonates can confirm these results, active vaccination with recombinant hepatitis B vaccines can be considered as a viable alternative to passive and active-passive immunization for the protection of neonates at high risk for hepatitis B infection. Indeed, the W H O has concluded that the simplest and most effective strategy for the control and eventual eradication of H BV in Southeast Asia and the Pacific would be to immunize all newborns with hepatitis B vaccine only 19 By disposing of the need for maternal screening and the expensive use of HBIg, the cost of hepatitis B immunization programmes based on vaccination of all newborns in regions of high hepatitis B endemicity can be considerably reduced. To this end, the results obtained in this study are particularly encouraging.

References 1 Ghendon, Y. Perinatat transmission of hepatitis B virus in high-incidence countries. J. Viral. Methods 1987, 17, 69 2 Okada, K., Kamiyama, I., tnomata, M., Imai, M, Miyakawa, Y. and Mayumi, M. e Antigen and anti-e in the serum of asymptomatic carrier mothers as indicators of positive and negative transmission of hepatitis B virus to their infants. N. Engl. J. Med. 1976, 294, 746 3 Beasley, R.P., Trepo, C., Stevens, CE. and Szmuness, W. The antigen and vertical transmission of hepatitis B surface antigen. Am. J. Epidemiol. 1977, 105, 94 4 Lee, A.K.Y., Ip, H.M.H. and Wang, V.C.W. Mechanisms at maternal-fetal transmission of hepatitis B virus. J. Infect. Dis. 1978, 138, 668 5 Beasley, R.P., Hwang, L.Y., Lee, G.C.Y. et al. Prevention of perinatally transmitted hepatitis B virus infections with hepatitis B immune globulin and hepatitis B vaccine. Lancet 1983, li, 1099 6 Wang, V.C.W., ip, H.M.H., Reesink, H.W. et al. Prevention of the HBsAg carrier state in newborn infants of mothers who are chronic carriers of HBsAg and HBeAg by administration of hepatitis B immunoglobulin. Lancet 1984, i, 921 7 Xu, Z.Y., Liu, C.B, Francis, D.P. et al. Prevention of perinatat acquisition of hepatitis B virus carriage using vaccine: preliminary report of a randomized, double-blind placebo-controlled and comparative trial. Pediatrics 1985, 76, 713 8 Iwarson, S.A. Chronic hepatitis B. in: Hepatitis B (Ed. Gerety, R.J) Academic Press Inc., Orlando, FL, USA, 1985, pp. 119-153 9 Tabor, E. Hepatitis B virus and primary hepatocellular carcinoma In: Hepatitis B (Ed. Gerety, R.J.) Academic Press Inc., Orlando, FL, USA, 1985, pp. 247-267 10 Goudeau, A., Lo, K.J. Coursaget, P. et ai. Prevention of hepatitis B virus infection in children born to HBsAg positive/HBeAg positive mothers: preliminary results of active and passive-active immunization. Dev. Biol. Stand. 1983, 54, 399 11 Lo, K.J., Tsai, Y.T., Lee, S.D. et al. Immunoprophytaxis of infection with hepatitis B virus in infants born to hepatitis B surface antigen-positive carrier mothers. J. Infect. Dis. 1985, 152, 817 12 Boxall, E.H. and Tarlow, M.J. Hepatitis B vaccine in the prevention of perinataUy transmitted hepatitis B virus infections: initial report of a study in the west midlands of England. J Med. Viral. 1986,18, 255 13 Farmer, K., Gunn, T. and Woodfield, D.G. A combination of hepatitis B vaccine and immunoglobulin does not protect all infants born to hepatitis B e antigen positive mothers. NZ Med. J. 1987, 100, 412 14 Poovorawan, Y., Sanpavat, S., Pongpunlert, W.. Chumdermpadetsuk, S., Sentrakul, P. and Salary, A. Protective efficacy of a recombinant DNA hepatitis B vaccine in neonates of HBe antigen-positive

Protective efficacy of hepatitis B vaccine in neonates: Y. Poovorawan et al. mothers. J. Am. Med. Assoc. 1989, 281, 3278 15 Harford, N., Cabezon, T., Colau, B., Delisee, A-M, Rutgers, T. and De Wilde, M. Construction and characterization of a Saccharomyces cerevisiee strain (RIT4376) expressing hepatitis B surface antigen. Postgrad. Med. J. 1987, 63 (suppl. 2), 65 16 P~tre, J., Van Wijnendael, F., De Neys, B. et al. Development of a hepatitis B vaccine from transformed yeast cells. Postgrad. Med. J. 1987, 63 (suppl. 2), 73 17 Hauser, P., Voet, P., Simoen, E. et al. Immunological properties

of recombinant HBsAg produced in ~;east. Postgrad. Med. J. 1967, (13 (suppl. 2), 83 18 Andre, F.E. and Safary, A. Clinical experience with a yeastderived hepatitis B vaccine. In: Viral Hepatitis and Liver Disease (Ed. Zuckerman, A.J.) Alan R. Liss, Inc., New York, USA, 1968, pp. 1025--1030 19 WHO Report. Meeting of the Task Force on Hepatitis B. Regional Office for the Western Pacific, Manila, Philippines, March 1984, 1-15

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