By
Liz Highleyman
An
effective and widely available hepatitis B vaccine (brand
names Recombivax HB and Engerix-B, and a combination hepatitis
A and B vaccine, Twinrix) prevents HBV infection due to mother-to-child
transmission, contact with blood, sexual contact, or other
routes.
The HBV vaccine first became commercially available in the
early 1980s and was added to the routine infant immunization
series in the U.S. starting in 1991, with the first of 3 doses
given soon after birth.
Vaccination is also recommended for adolescents who were not
vaccinated as babies and for adults at risk, including healthcare
and public safety workers, injection drug users, men who have
sex with men and all sexually active people who are not in
long-term monogamous relationships, travelers to high-prevalence
regions, household members of people with chronic hepatitis
B, residents of institutions such as prisons and long-term
care facilities, and people with chronic hepatitis C (since
having both B and C simultaneously can lead to worse liver
disease).
Annemarie Wasley from the CDC and colleagues assessed trends
in the prevalence of HBV infection in the U.S. after the widespread
adoption of hepatitis B vaccination. The investigators determined
the prevalence of HBV infection and immunity (due to vaccination
or previously having and clearing the virus) in a representative
sample of the population during 1999-2006 and 1988-1994 using
data from the National Health and Nutrition Examination Surveys
(NHANES).
Participants age 6 years and older were tested for antibodies
to hepatitis B core antigen (anti-HBc), hepatitis B surface
antigen (HBsAg), and antibodies to hepatitis B surface antigen
(anti-HBs). Briefly, people who are positive for both anti-HBc
and anti-HBs are immune due to natural infection, those who
are anti-HBc negative but anti-HBs positive are immune due
to vaccination, those who are HBsAg and anti-HBc positive
but anti-HBs negative have current infection, and those negative
for all 3 markers are susceptible to infection. (See this
chart for more information.)
| Interpretation
of Hepatitis B Serologic Test Results |
| Tests |
Results |
Interpretation |
HBsAg
anti-HBc
anti-HBs |
negative
negative
negative |
Susceptible |
HBsAg
anti-HBc
anti-HBs |
negative
positive
positive |
Immune
due to natural infection |
HBsAg
anti-HBc
anti-HBs |
negative
negative
positive |
Immune
due to Hepatitis B vaccination |
HBsAg
anti-HBc
IgM anti-HBc
anti-HBs |
positive
positive
positive
negative |
Acutely
infected |
HBsAg
anti-HBc
IgM anti-HBc
anti-HBs |
positive
positive
negative
negative |
Chronically
infected |
HBsAg
anti-HBc
anti-HBs |
negative
positive
negative |
Interpretation
unclear; four possibilities:
| 1. |
Resolved
infection (most common) |
| 2. |
False-positive
anti-HBc, thus susceptible |
| 3.
|
"Low
level" chronic infection |
| 4.
|
Resolving
acute infection |
|
| Hepatitis
B surface antigen (HBsAg): A protein on the surface
of HBV; it can be detected in high levels in serum during
acute or chronic HBV infection. The presence of HBsAg
indicates that the person is infectious. The body normally
produces antibodies to HBsAg as part of the normal immune
response to infection. HBsAg is the antigen used to make
Hepatitis B vaccine.
Hepatitis
B surface antibody (anti-HBs): The presence
of anti-HBs is generally interpreted as indicating recovery
and immunity from HBV infection. Anti-HBs also develops
in a person who has been successfully vaccinated against
Hepatitis B.
Total Hepatitis B core antibody (anti-HBc):
Appears at the onset of symptoms in acute Hepatitis
B and persists for life. The presence of anti-HBc indicates
previous or ongoing infection with HBV in an undefined
time frame.
IgM antibody to Hepatitis B core antigen (IgM anti-HBc):
Positivity indicates recent infection with HBV (≤6
months). Its presence indicates acute infection.
Adapted
from: A Comprehensive Immunization Strategy
to Eliminate Transmission of Hepatitis B Virus Infection
in the United States: Recommendations of the Advisory
Committee on Immunization Practices. Part I: Immunization
of Infants, Children, and Adolescents. MMWR 2005;54(No.
RR-16).
|
A
total of 21,260 NHANES 1988-1994 participants and 29,828 NHANES
1999-2006 participants age 6 and older were interviewed, examined,
and tested for anti-HBc and HBsAg. Blood samples were collected
for children age 2-5 starting in 1999, but participation in
this age group was low with only 3592 total participants,
just over half of whom had samples available for testing.
Results
 |
During
1999-2006, the overall age-adjusted prevalence of past
and present HBV infection (anti-HBc positivity) was 4.7%. |
|
The
1999-2006 overall age-adjusted prevalence of chronic HBV
infection (HBsAg positivity) was 0.27% |
|
Both
of these prevalence rates were statistically similar to
those during 1988-1994 (5.4% and 0.38%, respectively).
|
|
The
prevalence of anti-HBc positivity decreased significantly
among younger people, but not among those age 50 or older: |
| |
 |
Age
6-19: decrease from 1.9% in 1988-1994 to 0.6% in
1999-2006 (P < 0.01); |
|
Age
20-49: decrease from 5.9% to 4.6%, respectively
(P < 0.01); |
|
Age
50 and older: non-significant increase from 7.2%
to 7.7%, respectively. |
|
|
During
1999-2006, the prevalence of anti-HBc positivity differed
considerably across racial/ethnic groups (all ages combined): |
|
Whites
(non-Hispanic): 2.8%; |
|
Mexican-Americans:
2.9%; |
|
Blacks
(non-Hispanic): 12.2%; |
|
"Other,"
including Asians and non-Mexican Hispanics: 13.3%. |
|
|
Anti-HBc
prevalence was about 3 times higher among foreign-born
participants (12.2%) than U.S.-born participants (3.5%).
|
|
Among
U.S.-born children in the 6-19 age group, however, anti-HBc
prevalence -- 0.5% overall -- did not differ according
to race/ethnicity. |
|
Disparities
between U.S.-born and foreign-born children were smaller
during 1999-2006 (0.5% vs 2.0%) compared with 1988-1994
(1.0% vs 12.8%). |
|
Foreign-born
children of "other" race/ethnicity experienced
a > 90% decrease in anti-HBc prevalence between 1988-1994
and 1999-2006. |
|
Among
children age 6-19 years, 56.7% showed markers of vaccine-induced
immunity, with little difference across racial/ethnic
groups. |
Based
on these findings, the researchers concluded, "HBV prevalence
decreased among U.S. children, which reflected the impact
of global and domestic vaccination.
However, they continued, HBV prevalence "changed little
among adults," and approximately 730,000 U.S. residents
are chronically infected.
In particular, they elaborated in their discussion, foreign-born
residents made up 14% of NHANES participants during 1999-2006,
but accounted for 43% of HBV infections. This type of disparity
was not evident among children, however, suggesting that U.S.-
and foreign-born residents alike, as well as all racial/ethnic
groups, are receiving recommended hepatitis B vaccinations.
"[A] decade after universal vaccination of U.S. children
against hepatitis B began in 1991, we demonstrate a significant
reduction of 68% in HBV infection prevalence among children,
including those born in the United States and elsewhere,"
the authors wrote. "In addition, a 79% decrease in the
prevalence of chronic infection in this age group, although
based on a small number of children and not statistically
significant, further suggests that substantial progress has
been made in reducing the disease burden among children."
With regard to adults, they wrote, "The large burden
of chronic HBV infection among adults demonstrated by NHANES
highlights the need to improve screening programs and other
efforts to identify chronically infected persons, most of
whom remain asymptomatic until cirrhosis or end-stage liver
disease develops. Screening and counseling programs are important
to educate and medically manage infected patients to prevent
liver disease progression and to identify and vaccinate susceptible
contacts to interrupt further transmission."
National Center for HIV/AIDS, Viral Hepatitis, STD, and
TB Prevention, Centers for Disease Control and Prevention,
Atlanta, GA; National Center for Health Statistics, Centers
for Disease Control and Prevention, Hyattsville, MD; School
of Public Health, University of Medicine and Dentistry of
New Jersey, Piscataway, NJ.
7/2/10
Reference
A
Wasley, D Kruszon-Moran, W Kuhnert, and others. The prevalence
of hepatitis B virus infection in the United States in the
era of vaccination. Journal of Infectious Diseases
202(2): 192-201 (Abstract).
July 15, 2010.
