Chauhan AR
Pregnant women are vulnerable to many communicable and
non- communicable diseases; either the susceptibility to or severity of
infections increases due to pregnancy. Vaccination programmes are one of the
most important and cost effective health interventions. Fear of adverse effects
makes clinicians and mothers hesitant to vaccinate in pregnancy and the
obstetrician is only attuned to administering tetanus toxoid (TT); this article
addresses the recent recommendations for vaccination of pregnant and postpartum
women with Td (tetanus and diphtheria), Tdap (Tetanus toxoid, reduced
diphtheria toxoid and acellular pertussis vaccine), influenza and other
vaccines.
General guidelines for vaccination of pregnant women
include evaluation for the possibility of pregnancy before immunization and
immunization history. As a rule, live viral vaccines are contraindicated during
pregnancy; however this risk is largely theoretical. The benefits of
vaccinating pregnant women are usually greater than the potential risks when
the possibility of exposure to that particular infection is high, when the
infection would possibly harm the mother or fetus or when the vaccine is
unlikely to harm them. Inactivated viral vaccines, bacterial vaccines and
toxoids are safe in pregnancy. Women who have inadvertently received live
vaccine during pregnancy should not be counseled to terminate the pregnancy for
teratogenic risk; however non pregnant women who have received live vaccine
should delay pregnancy for at least 4 weeks. This is a change from the previous
recommendation of avoidance of pregnancy for 3 months. Another important point
of intervention is the postpartum period, where breast feeding women can be
immunized safely.
Td
Both tetanus and diphtheria toxoids (Td) and TT
vaccines have been used extensively in pregnant women worldwide to prevent
neonatal tetanus; their administration has not been shown to be teratogenic.
Current recommendation is that everyone should be given a booster shot for
tetanus and diphtheria every 10 years after first being immunized; hence Td
during pregnancy has replaced TT in many parts of the world.
Tdap
Pertussis is a highly contagious respiratory infection
caused by Bordetella pertussis which colonises respiratory tract mucous
membranes, produces toxins that damage mucosa and induce systemic effects; the
typical spasms of coughing ending with a “whoop”. Both the incidence and
mortality are underestimated and underreported. Older individuals, especially
parents, represent a reservoir of infection transmitting disease to
unvaccinated or partially vaccinated infants. Despite generally high coverage
with childhood pertussis vaccines, it is one of the leading causes of deaths
worldwide. In recent years, a decrease in diphtheria– pertussis–tetanus (DPT)
vaccine compliance has been reported from different parts of India
“Cocooning” is the strategy of vaccinating parents,
siblings, grandparents, and health workers who are likely to have close contact
with an infant aged <12 months. These contacts, especially pregnant women in
the later part of pregnancy or immediately postpartum should receive Tdap to
reduce the risk for transmission of pertussis to infants, ideally at least 2
weeks prior to the anticipated contact. Tdap is a combination vaccine that
contains tetanus (T), diphtheria (d) and acellular pertussis (ap) in a single
injection, and provides protection against all three; it is approved for
adolescents from the age of 11 (younger contacts should receive DTaP) and
adults ages 19 to 64. There is no live vaccine component in Tdap. Some studies
have suggested that maternal antibodies to pertussis can inhibit production of
active pertussis-specific antibody after administration of DTaP vaccine to
infants of mothers vaccinated with Tdap during pregnancy, referred to as
“blunting”. However, the benefit of protection given by maternal antibodies in
newborn infants is much higher than the risk of shifting the burden of the
disease to later in infancy.
It is recommended to give one dose of Tdap during each
pregnancy irrespective of the patient’s prior history of receiving Tdap.
Although Tdap may be given at any time during pregnancy, the ideal time for
administration is between 27 and 36 weeks’ of gestation, which maximizes the
maternal antibody response and transfer of antibodies to the neonate. The first
dose of TT should be replaced with Td and the second, with Tdap. If Tdap is not
administered during pregnancy, it should be administered soon after delivery.
Along with several international agencies like Advisory Committee on
Immunization Practices (ACIP) of CDC, Indian Academy
Influenza
Influenza is a highly contagious acute respiratory
illness caused by infection with influenza viruses (Orthomyxoviridae) which
affects the upper and lower respiratory tracts and produces systemic signs and
symptoms. Three types, Influenza A, B and C are determined by nuclear material.
Influenza A subtypes are further divided based on H and N surface
glycoproteins.
“Flu” is often mistaken for the common cold, but has
serious and far reaching complications. Global pandemics and epidemics cause a
huge disease burden; though pregnancy does not increase susceptibility to
influenza infection, pregnant women in the second and third trimesters of
pregnancy are at increased risk for hospitalization, severe illness, serious
complications like pneumonia and death. Maternal influenza infection has also
been associated with an increased risk of schizophrenia (which is higher with
first trimester exposure) in the offspring. There is also an increased risk of
preeclampsia in mothers and preterm labor, low birth weight, lower Apgar scores
at birth and stillbirth. It is critical to vaccinate against influenza before
the season begins; however this cannot be predicted accurately due to
geographical and other variations. Hence routine influenza vaccination is
recommended for all women who are or will be pregnant (in any trimester) during
influenza season. In case of outbreaks of influenza prior to the season,
vaccination should be given to all pregnant women. A single dose of the
trivalent inactivated vaccine (TIV) intramuscularly is recommended; the live
attenuated nasal spray is contraindicated in pregnancy. Immunization to the
mother affords protection to the infant for at least the first 6 months of
life. ACOG guidelines state that “preventing influenza during pregnancy is an
essential element of prenatal care, and the most effective strategy for
preventing influenza is annual immunization”. This is endorsed by many other
agencies including WHO, ACIP (CDC) and Indian Association of Physicians (API).
Hepatitis B
Hepatitis B poses a serious risk to infants at birth
and universal screening with HBsAg for all pregnant women is recommended.
Pregnant women who are considered as being at risk of developing HBV infection
during pregnancy (more than one sex partner during the preceding 6 months,
evaluated or treated for an STI, recent or current intravenous drug abuse, or
an HBsAg-positive sex partner) should be tested with antibody to surface
antigen (anti –HBs) and be vaccinated if negative. Vaccination should be given
only if clearly needed and possible advantages outweigh the possible risks. There
are limited data which suggest that developing fetuses are not at risk for
adverse events following hepatitis B vaccine. Babies should get HBIG at birth
and first dose of vaccine within 12 hours of life.
HPV vaccine
HPV vaccines are not recommended for use in pregnant
women. If a woman gets pregnant after initiating the vaccination series, no
intervention is needed but the remainder of the 3-dose series should be delayed
until completion of pregnancy.
Postpartum vaccination
The puerperal period is an excellent opportunity for
vaccination and promotion of positive health advice. It is safe for a woman to
receive routine vaccines after birth and in the lactation period. A woman who
has not received Tdap or influenza vaccine should be vaccinated right after
delivery and a woman who is not immune to measles, mumps and rubella and/or
varicella (chicken pox) should be vaccinated before she leaves the hospital.
HPV vaccine is also safe during the lactation period.
In conclusion, maternal vaccination is a
cost-effective and targeted strategy to improve pregnancy outcomes in developed
and developing countries. Many national organizations like IAP, Indian
Association of Physicians (API) and FOGSI, and all international public health
agencies recommend vaccination during pregnancy for influenza and Tdap. Lack of
awareness of benefits and concerns about vaccine safety in pregnancy are common
barriers to vaccination. The real challenge is to educate health professionals
and make these vaccinations routine.