Elsevier

Vaccine

Volume 19, Issues 28–29, 16 July 2001, Pages 4081-4085
Vaccine

Evaluation of the response to a booster dose of hepatitis B vaccine in previously immunized healthcare workers

https://doi.org/10.1016/S0264-410X(01)00112-8Get rights and content

Abstract

Introduction: Hepatitis B vaccination is recommended for all healthcare workers (HCW) at risk of exposure to infectious body fluids. However, the absolute duration of protection from immunization is unknown. The purpose of this randomized comparison trial was to determine how previously immunized HCW respond to different booster doses of hepatitis B vaccine. Method: Adult HCW (n=59) were classified by level of hepatitis B surface antigen (anti-HBs), either <10 milli-International Units per milliliter (mIU/ml) or 10–50 mIU/ml. Participants were then randomized to receive a 2.5 or 10 μg dose of hepatitis B vaccine. Evaluation of anti-HBs levels were conducted 10 to 14 days, one month and one year postbooster. Results and discussion: All participants responded to the booster dose with increased anti-HBs levels. At 14 days, mean anti-HBs levels were significantly higher for those with higher levels at baseline (P=0.004) and those receiving the 10 μg dose (P=0.016). At one month, those with higher anti-HBs levels at baseline and those receiving the 10 μg dose were significantly higher (P<0.01 for both). At one year, the increase for the higher dose was no longer statistically significant when examined by itself (P=0.081); statistical significance (P=0.021) was achieved after adjusting for anti-HBs level at baseline. For all participants, the geometric mean anti-HBs level was 2618 mIU/ml at 14 days, 2175 mIU/ml at one month and 88.9 mIU/ml at one year. At all time points the increase in anti-HBs levels represented an increase over the geometric mean baseline level of anti-HBs (7.4 mIU/ml). Hepatitis B immunized adults responded to a booster dose of hepatitis B vaccine from 3 to 13 yr postvaccination series. Data support current recommendations that immunized HCW do not require periodic antibody testing or vaccine boosters.

Introduction

Healthcare workers (HCW) are at increased risk of hepatitis B virus (HBV) infection, primarily from occupational exposure to infectious body fluids from persons with chronic infection [1], [2]. In the USA, it is estimated that over one million persons are chronically infected with HBV [3] and these persons represent an ongoing risk of infection to HCW. Safe and effective vaccines to prevent HBV infection were licensed in 1981 and have been commercially available since 1982 [4]. In 1982, it was recommended that HCW at risk of occupational exposure to HBV be vaccinated [5]. Given this recommendation and a mandate for employers to offer vaccination to this at-risk group [6], the number of HCW who are HBV-vaccinated has increased [7], [8]. However, the absolute duration of protection from immunization is unknown.

Many HCW may have received their primary hepatitis B vaccine series over 10 yr ago. Studies of long-term persistence of antibody indicate that adults who responded to the initial vaccine series may lose measurable antibody to hepatitis B surface antigen (anti-HBs) within 10 yr of immunization [9]. However, follow-up studies of immunized adults and children indicate that a single 3-dose vaccination series prevents HBV infection for up to 15 yr, including after loss of detectable antibody [10].

We conducted a randomized comparison trial to determine how HCW who previously responded to hepatitis B immunization, but subsequently had undetectable or low anti-HBs levels, would respond to a 2.5 or 10 μg booster dose of hepatitis B vaccine.

Section snippets

Method

The trial was conducted (1994–1995) at the Alaska Native Medical Center (ANMC), a tertiary care hospital located in Anchorage, Alaska, USA. The Alaska Area Native Health Service and Indian Health Service Institutional Review Boards approved the trial and participants granted informed consent.

Potential trial participants were identified through a comprehensive review of ANMC HCW medical records. Persons’ recruited were those evidencing (1) previous administration, as an adult, of 3 doses of

Results

Of the 115 participants who met the initial entry criteria, 48 (42%) were excluded as their baseline anti-HBs levels were >50 mIU/ml, 8 (7%) were lost to enrollment, 1 (<1%) only completed the first follow-up blood draw, and 58 (50%) completed all follow-up blood draws. Fig. 1 further illustrates number of participants randomized and followed-up by baseline anti-HBs level and booster dose administered. Demographic characteristics of participants (n=59) include: female, 39 (66%); Alaska Native,

Discussion

Our trial demonstrated that adults with undetectable or low anti-HBs level, 3 to 13 yr after receiving the 3-dose hepatitis B vaccine series, responded to a booster dose of vaccine. Fourteen days after either a low or high booster dose of vaccine antigen, nearly all participants had levels of antibody that ranged from 10 to >100 mIU/ml, indicating this was an anamnestic response to HBsAg.

The higher booster dose of vaccine resulted in a generally higher anti-HBs response when compared to the

Acknowledgements

For their contribution to this work the following are acknowledged: Leslie Fox-Leyva, Mary Snowball and Harvey Tanttila. Use of brand names is for identification purposes only and does not imply endorsement by the US Public Health Service or the US Department of Health and Human Services.

References (15)

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