Hepatitis B Vaccination in Premature and Low Birth Weight (LBW) Babies

August 22, 2002

Sheila Bhave, Snehalata Bhise, Sanjay C. Chavan, S.S. Naik*, Raju V.L.N.

Pusapati+, Ashish Bavdekar, Anand Pandit From the Department of Pediatrics,

KEM Hospital, Pune 411 011,*Department of Biochemistry & Endocrinology, KEM

Hospital, Pune 411 011 and +Shantha Biotechnics Pvt. Limited, Hyderabad 500

034, India. Correspondence to: Dr. Sheila Bhave, Consultant in Pediatric

Research, Department of Pediatrics, KEM Hospital, Pune 411 011, India.

E-mail: kemhrc@...

Manuscript received: December 24, 2001, Initial review completed: February

12, 2002, Revision accepted: April 9, 2002.

Objective: To assess the immune response of preterm and low birth weight

babies (LBW) to hepatitis B (HB) vaccine. Setting: Neonatal Intensive Care

Unit (NICU), postnatal ward and follow up clinics of KEM Hospital, Pune.

Design: Open trial. Methods: 100 babies were enrolled in four study groups.

Group I - preterm, gestational age (GA) < 34 weeks; Group II - GA 34 to 36

weeks; Group III full term <2.5 kg (LBW babies); and Group IV full term >2.5

kg (controls). A recombinant DNA HB vaccine was given at 0, 1, 2 and 12

month schedule. The first injection was administered as soon as the neonate

was stabilized. Immune response in terms of anti HBs titres (AUSAB EIA

Diagnostic kit) was measured one month after each of the first three

injections and at the time of one year booster. Adverse events were

monitored. Results: 88 and 62 babies completed the study till the third dose

and one year booster dose respectively. Immune response of HB vaccine was

uniformly good in all the study groups with 100% sero-conversion after the

second dose itself. By one year (i.e. before the booster dose), very high

titres were recorded in all 100%, with 85% demonstrating titres >1000

mIU/ml. Preterm and LBW babies had higher GMT as compared to full term

babies till one month after third dose. By one year (before booster), full

term babies had higher GMT than preterm and LBW babies. However, these

differences were not statistically significant. The vaccine was well

tolerated and safe and there were no adverse reactions. Conclusions: Immune

response of preterm, LBW and full term babies to the new generation

recombinant DNA HB vaccine was uniformly good. High and long term

seroprotective levels were achieved after the second dose itself.

Key words: Hepatitis B vaccine, Preterm immunization.

IN 1991, the WHO Global Advisory Group

recommended that hepatitis B (HB) vaccine should be integrated into the

national immunization schedule (EPI) of all countries by the year 1997(1).

As of date, 130 countries have reportedly adopted the recom-mendations(2).

Despite endorsement of the recommendations by the Indian Academy of

Pediatrics, financial constraints have delayed its implementation on a

national basis(3). However, many state and non government organizations are

already providing the facility widely. With the recent availability of much

cheaper indigenously produced vaccines, 'universal' immunization with HB

vaccine may soon become a reality.

It is clear from many studies that for control of perinatal transmission,

the first dose of HB vaccine must be given soon after birth preferably

within 48 h(4). What still needs to be resolved is whether or not preterm

and low birth weight (LBW) babies can be included in the policy of universal

immunization starting at birth. The confusion has arisen chiefly because of

conflicting reports of the immune response in preterms; and because the

American Academy of Pediatrics (AAP) in 1994 revised its earlier

recommendations and advised delaying the initiation of HB vaccine in

preterms with a birth weight less than 2 kg till the age of 2 months(5). In

India, more than 30% of newborns are less than 2.5 kg at birth, and many are

less than 2 kg. Further, most of these babies have intrauterine growth

retardation (IUGR) rather than true prematurity. Is this policy of delaying

the first dose justified in our LBW babies, especially vis-a-vis the risk of

confusing field workers?

The aim of this study was to determine the immune response of preterm and

LBW babies to a new generation, recombinant DNA, HB vaccine in comparison to

full term neonates.

Subjects and Methods

The study was conducted in the Neonatal Intensive Care Unit (NICU) and

postnatal wards of KEM Hospital, Pune. 100 neonates were enrolled in four

study groups as seen in Table 1. {Group 1 = preterm, gestational age (GA) <

34 weeks; Group II = preterm, GA 34 to 36 weeks; Group III = full term <

2500 g IUGR babies, Group IV = full term, normal weight > 2500 g}. Parents

were counseled and only those willing for all four injections and blood

sampling were enrolled.

Table I- Clinical Characteristics and Age at First Injection

Gestational Age Group I < 34 weeks Group II 34 - 36 weeks Group III > 36

weeks LBW Group IV Term, normal weight

No. enrolled 25 25 25 25

Completed Study

Upto 3rd dose 21 18 25 24

Upto one year 14 13 19 16

Birth Weight (g)* 1489 ± 217 (1155 - 1920) 1842 ± 230 (1480 - 2422) 2051 ±

248.5 (1500 - 2450) 2741 ± 244.7 (2530 - 3575)

Female/male 10/11 6/12 17/8 11/13

Hyperbilirubinemia 13 6 4 2

Sepsis 13 5 2 1

Respiratory distress 7 1 - -

Necrotising enterocolitis 7 3 - -

Others 6 1 1 1

Age (days) at first dose* 202 ± 8.4 (4 -30) 10.2 ± 6.3 ( 3 -25) 7.7 ±4.2

(2 - 16) 1.4 ± 3.5 (0 - 15)

Others include intraventricular hemorrhage, hypoglycemia, congenital heart

disease, anemia, transient

tachypnea and seizures.

*Mean ± SD (range)

A new generation yeast derived recombinant DNA HB vaccine (Shanvac B,

Shantha Biotechnics, Hyderabad) at a dose of 0.5 ml (10 mg) was given at 0,

1 month, 2 months and 12 months. All injections were given in the

antero-lateral side of thigh. Medical Social Workers (MSW) encouraged

compliance with counseling and home visits. The zero dose was given in the

NICU or ward as soon as the baby was considered 'stable'. The subsequent

doses were given in follow up clinics. After each dose of the vaccine babies

were monitored for any evidence of adverse reaction such as anaphylaxis,

fever, local pain, erythema, tenderness, induration, vomiting etc. Adverse

reactions were graded as 0-absent, 1-mild, 2-moderate, 3-severe. Monitoring

for reaction was done by staff members of the NICU and ward after 0 dose.

For subsequent doses, the baby was observed in the follow up clinics for

half-hour after the injection for any immediate reactions like anaphylaxis.

Further monitoring (for 48 h) was carried out by parents at home (parents

were informed about the possibility of above mentioned side effects and

advised to report, if any). The MSW made a phone call after 48 h to confirm

the absence of side effects.

Serum samples for antibody estimation were obtained one month after the

first, second and third dose and just before the 12 months dose. All samples

were taken by venepuncture in upper limb under all aseptic precautions.

Anti-HBs titres were assessed quantitatively by microparticle enzyme

immunoassay (AUSAB EIA kits, Abbott Laboratories). The laboratory personnel

were blinded to the subjects' identity. All the samples (four sets) were

tested in two batches of kits. For internal (batch) validity, two samples

(lab controls) were tested in both the batches. The result were stable.

Levels of anti HBs > 10 mIU/ml were taken as evidence of seroprotection

while levels > 100 mlU/ml were considered as evidence of long term

seroprotection(6). Samples positive for anti HBs were included for

calculation of geometric mean titre (GMT). Students 't' test was used to

compare anti HBs GMT between various groups.

The study was approved by the Ethical Committee of our center. Free and

informed written parental consent was obtained in all cases.

Results

Of the 100 enrolled babies, 88 completed the study upto one month after the

third dose of vaccine, and 62 completed the entire study i.e., upto the end

of 12 months (last dose). The reasons for the drop out in the first phase

were: death (n = 4), transfer (n = 4), refusal (n = 2), lost to follow up (n

= 2). The further drop outs were due to death (n = 5), transfer (n = 11),

refusal (n = 4) and lost to follow up (n = 6). All deaths were related to

complications of prematurity and LBW.

Clinical parameters of the study subjects are seen in Table I. There were no

demographic differences between babies who completed the study and those who

did not. Associated illnesses or problems in the study groups are seen in

Table I.

Age of initiation of first dose of vaccine: The age at first dose of

vaccination ranged from 4 - 30 days in the smallest weight group and 0 - 15

days in the full term normal weight group with a mean of 8.0 ± 7.8 days for

the whole group.

Side effects: There were no adverse reactions or side effects after any of

the doses throughout the entire study. None of the deaths were related to

vaccinations.

Seroprotection: Seroprotection (i.e., anti HBs antibodies > 10 mIU/ml), at

one month after the first dose were 67%, 57%, 70%, and 50% in groups I, II,

III and IV respectively. Seroprotection was 100% in all groups 1 month after

the second dose, and remained 100% after the third and before the last dose.

Antibody titres had reached long term protective levels (>100 mIU/ml) in 54

of the 88 babies (61%) after the second dose, in 84 of the 88 babies (95%)

by the end of third dose and in all 62 babies (100%) at one year. At one

year, 85% subjects had achieved antibody titres > 1000 mIU/ml.

Geometric mean titres (GMT): Serial GMT of anti HBs antibodies in different

groups are seen in Fig.1. All the study groups showed modest increase of GMT

after the second dose (post one month dose) itself. GMT rose further after

the third dose reaching a mean of 452 mIU/ml in preterm (Group I and II) and

334 mIU/ml in full term babies (Group III and IV). LBW babies (Group I, II,

III) had a higher GMT of 415 mIU/ml as compared to 304 mIU/ml in normal

weight babies (Group IV); differences between various groups were not

significant. At one year (before last dose), GMT showed more then 5 fold

increase in antibody titres in all the 62 babies followed up. None of the

babies showed decreasing titres. On the whole GMT at 1 year were higher in

normal weight (Group IV - 2854 mIU/ml) control babies than the LBW (Group I,

II and III - 1814 mIU/ml) babies (p = 0.08). Similarly GMT were higher in

full term babies Group III and IV as compared to preterm Group I and II

(2,357 mIU/ml in full term vs. 1,690 mIU/ml in preterms respectively) (p =

0.18).

Discussion

The main aim of this study was to evaluate the immune response of preterm

and LBW babies to HB vaccine. We enrolled 100 babies with gestational ages

ranging from 27 weeks to 40 weeks and with birth weights ranging from 1155 g

to 3575 g. We used the schedule specifically recommended for high risk

babies namely four doses at 0, 1, 2 and 12 months. Despite the high

mortality rate in the small preterms and despite transfer of residence in

many we achieved a high compliance rate with 88% and 62% completing the

study upto the third and last dose respectively.

The immune response to HB vaccine in our study was uniformly good in

preterms, IUGR babies and normal weight neonates. The overall seroconversion

rate was 100% with remarkably high titres reaching well above 1000 mIU/ml in

85% by the one year booster dose (mean GMT of whole group 2040 mIU/ml). In

other studies using HB Vax(7) and Engerix B(8), the final GMTs did not cross

500 mIU/ml and 750 mIU/ml respectively. The very high and 'long term sero

protective level' achieved in our study are due to the very high

immunogenecity of the vaccine used. Previous studies using this vaccine have

also reported much higher titres and protective levels as compared to other

recombinant DNA vaccines(9).

The immune response was more than satisfactory in all the study groups with

high GMT at all stages of testing. Preterm babies, infact, had higher GMT as

compared to full term babies until one month after the third dose. By age

one year and before the fourth dose, full term babies had higher GMT than

preterms. The IUGR group too, showed good immunological response throughout

the study. Though there are no reported studies from India, data from other

countries (both developing and developed) regarding immune response in

preterms is conflicting(10,11). Huang, et al,(9) Blondecham, et al(8) and

others(12-14) have shown less than 90% seroprotection with low GMT in

preterms at the end of their schedule, especially, in small preterms <1500

g. An interesting study in small preterms suggested better immune response

if first dose was delayed till 30 days of age(15). Other studies have

reported excellent response in preterm babies irrespective of birth weight

or age of first injection(16). The varying results could well be due to

differences in ethnicity, type of vaccine used and the timing of the first

vaccination.

It has been suggested recently that the first dose of HB vaccine should be

delayed to 6 to 8 weeks, the advantage being (a) possibility of combination

with DPT (and also Hib vaccine), thereby reducing the number and cost of

injection(18, 19) and ( better immune response in preterms and babies with

IUGR if initiation is delayed(15). However, it is important to remember that

India is in the intermediate to high risk zone for HBV and perinatal

transmission can be halted effectively only if vaccination commences within

48 h of birth(4,17). In our smallest preterm group with mean birthweight

<1500 g, the first dose of vaccine was delayed in some as long as 30 days

mainly because, as per protocol, the vaccine was given only after the baby

was stable. These were NICU patients with serious clinical problems

including sepsis and respiratory distress. In other babies, who were not so

ill, the first dose was given as early as four days of life. We found no

difference in the immune response in these babies. However, whether, 'sick'

neonates can be given the vaccine within 48 hr of birth without waiting for

'stabilization' remains to be seen. If possible, it would be particularly

advantageous as these are the high risk groups, receiving multiple

transfusions, blood products and injections in the NICU.

The 0, 1, 2 and 12 schedule used in our study was obviously very effective.

All the babies (100%) seroconverted after the second dose itself (with more

than 60% reaching 'long term seroprotective levels'). This suggests that the

third dose (at second month) is probably unnecessary even in preterms, LBWs

and other high risk babies. Interestingly, in our study, antibody titres

showed more than a five fold increase between the third and last dose, even

though no further injections were given during this period. Obviously, once

stimulated antibodies continue to increase with time; boosters accentuate

the increase.

The vaccine was well tolerated in all subjects and there were no adverse

reactions. The safety of the vaccine in normal neonates and adults has been

reported previously(9,16).

Acknowledgement

We thank our Medical Social Workers for diligently following up the babies.

Contributors: ShB designed the study and drafted the paper and will act as

guarantor. SnB and SC conducted the study. SN carried out the antibody

testing. AB helped in analysis and interpretation of the data. AP and RP

helped in designing the study and monitored the project.

Funding: Shantha Biotechnics Pvt. Ltd., Hyderabad.

Competing interests: RP is an employee of Shantha Biotechnics Pvt. Limited,

a manufacturer of Hepatitis B vaccine.

Key Messages

.. Immune response of preterms, LBW and full term babies is uniformely good

to the new generation recombinant DNA hepatitis B vaccine.

.. Irrespective of the gestational age and birth weight, hepatitis B

vaccination can be started soon after birth. The immunization schedule can

be safely and effectively used for LBW babies.

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August 22, 2002