Parvathy Rajan

I am Dr.Parvathy Rajan, who writes about new medical researches, creativity, clinical scenarios, lifestyle and human conditions. I focus on things that are hard to examine but important to explore. I want to play my part in supporting the next generation of empowered newbies in the field of research and health.

VACCINATION IN CHILDREN INFECTED WITH HIV MOTHER

10 August 2021

Ideally HIV counselling and testing should be offered to all pregnant women, accompanied by provision of interventions to prevent mother-to-child transmission in those who test HIV antibody positive. However, it is recognized that counselling and testing facilities are often not available to all pregnant women in countries hardest hit by the HIV epidemic

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To prevent vertical transmission of HIV, it is essential to identify the maternal infection. Even the most thorough history and physical examination will identify fewer than half of the HIV-positive women. Therefore, routinely offering HIV testing to all pregnant women is recommended

Antiretroviral therapy for an HIV-infected woman should be chosen to offer the best therapy for the woman’s health while weighing the benefits and risks of the drugs for the fetus

Obstetrical factors have been shown to affect mother-to-child transmission of HIV, it was found that the duration of rupture of membranes was a major factor in the risk of perinatal transmission of HIV

The prevention of mother to child transmission of HIV has resulted in reduced burden of pediatric HIV-infection, but the prevalence of maternal HIV infection remains high in sub-Saharan African countries. HIV-exposed-uninfected infants have an increased risk of morbidity and mortality due to infectious diseases than HIV-unexposed infants, particularly during the first six months of life, which in part might be due to lower levels of pathogen-specific protective antibodies acquired transplacentally from their mothers. This could be mitigated by vaccinating pregnant women to boost antibody levels; although vaccine responses among HIV-infected pregnant women might differ compared to HIV-uninfected women. We reviewed studies that compared natural and vaccine-induced antibody levels to different epitopes between HIV-infected and HIV-uninfected pregnant women

The protection of the infants could either be due to prevention of mother-to-child transmission of pathogens during close contact, or through transfer of maternal epitope-specific protective antibodies via the placenta and/or breastmilk. This is especially beneficial against diseases presenting soon after birth, or during the initial vulnerable period prior to young infants completing their immunization against vaccine preventable diseases

vaccination of pregnant women in protecting their infants through transplacental antibody transfer depends on a number of factors such as: (i) the immunogenicity of the vaccine among pregnant women, (ii) baseline maternal antibody levels and underlying prevalence of memory lymphocytes, (iii) subclass of the antibodies induced by the vaccine, (iv) efficiency of transplacental antibody transfer, (v) adequate gestational time to allow for optimal in-utero transplacental transfer of antibodies, and (vi) antibody half-life in the women and infant

Vaccination during pregnancy aimed at protecting the infants, needs to induce sufficient maternal antibody levels that will be transferred to the fetus within the remaining gestational period; and persist in the infant through early infancy. The active transfer of maternal IgG antibodies (natural or vaccine-induced) occurs most efficiently in the third trimester of pregnancy.

more efficient transfer of antibodies occurs in the last weeks before birth, infants born to women vaccinated in the second trimester had higher levels of pertussis antibodies than those vaccinated in the third trimester

Generally, maternal and cord blood antibody concentrations are correlated; though higher maternal antibody concentrations and more efficient transplacental transfer are noted in mothers in high-income countries compared to low-income countries

IV-infected pregnant women have lower baseline/pre-vaccination antibody levels, including to epitopes of measles virus, influenza virus, Streptococcus pneumoniae, Haemophilus influenzae type b, GBS and tetanus compared to HIV-uninfected women

HIV-exposed uninfected infants less than six months have an increased risk of hospitalization and death from respiratory virus-associated lower respiratory tract infections, including influenza virus

the WHO has recommended all EPI vaccines (including BCG and Measles vaccine, as well as OPV) for infants born of HIV positive mothers, whose HIV infection status has not been determined and for known HIV infected children who are as yet asymptomatic. This guideline would apply to MMR also. In the United States OPV is not allowed in these children, more for theoretical reasons than from experience; the availability of IPV makes this option quite feasible.

The WHO does not recommend BCG in children with symptomatic HIV infection. Both under WHO EPI and in the United States, Measles vaccine (or MMR) is allowed even in symptomatic stage of HIV infection (except in the terminal phase), so as to prevent serious and life threatening wild measles virus disease. Experience with Varicella vaccine is limited; hence as a cautionary measure it is not given to known HIV infected children in the US. Since non-live typhoid vaccines are available, perhaps the same approach is possible with typhoid vaccines; in other words, perhaps we ought to avoid live oral typhoid vaccine in HIV infected children, unless sufficient data on safety emerges.

BCG VACCINATION FOR INFANTS AT RISK FOR HIV INFECTION

As in infants symptoms of HIV-infection rarely appear before several months of age, BCG vaccination should be administered to those infants regardless of HIV exposure, especially considering the high endemicity of tuberculosis in populations with high HIV prevalence.

Close follow-up of infants known to be born to HIV-infected mothers and who received BCG at birth is recommended in order to provide early identification and treatment of any BCG-related complication.

In settings with adequate HIV services that could allow for early identification and administration of antiretroviral therapy to HIV-infected children, consideration should be given to delaying BCG vaccination in infants born to mothers known to be infected with HIV until these infants are confirmed to be HIV negative.

Infants who demonstrate signs or reported symptoms of HIV-infection and who are born to women known to have HIV infection should not be vaccinated.

it remains uncertain whether HIV-exposed uninfected (HEU) infants have impaired responses to oral vaccines. Early immunization of HIV‐positive children was recommended even before the widespread availability of effective HAART based on the rationale that vaccine‐induced immunity could occur before immunosuppression had progressed.

After HAART initiation, immune reconstitution is biphasic . The early rapid phase of viral load decay over 6 months is associated with recovery of thymic activity, repopulation of the T‐cell compartment and recovery of functional responses. The second phase, 6–12 months into HAART with sustained virological suppression, enables improving CD4 cell count and function, with slower redistribution of CD4 subpopulations and reduced CD8 activation. HAART initiation at an early age appears to preserve memory function, allowing immunity to previously received vaccines to be retained, as well as the ability to mount adequate and sustainable responses to new vaccines.

Tetanus and diphtheria vaccines

These are inactivated toxoid vaccines, so are safe for immunocompromised children. Vaccine effectiveness is not assured, however. Several studies have evaluated the tetanus vaccine responsiveness of children and adolescents on HAART. Those who are immunosuppressed when starting HAART have reduced capacity to mount protective responses to toxoid antigens, especially during the first year on HAART

It is recommended that children infected with HIV/ AIDS follow an accelerated immunization schedule. The bacille Calmette–Guérin vaccine is the most commonly used vaccine in the world and is the only vaccine available for Mycobacterium tuberculosis but should not be used in HIV-infected children

The World Health Organization recommends the use of the oral polio vaccine in asymptomatic HIVinfected children in areas of the world where the inactivated polio vaccine is not available.

The measles and varicella vaccines are administered to HIV-infected children who are not severely immunocompromised. The hepatitis B virus vaccine is recommended for HIV-infected children. The yellow fever vaccine is recommended at 9 months of age and every 10 years thereafter for asymptomatic HIV-infected children living in or traveling to HIV-endemic areas of the world

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Diphtheria–Tetanus–Pertussis Vaccine

The diphtheria–tetanus–pertussis (DTP) vaccine is not contraindicated for HIV-infected children or their close contacts. Newer preparations of DTP vaccines using acellular pertussis (DTaP) for the primary series and booster doses or those including acellular pertussis for older adolescents and adults (Tdap) are available in many countries. When available, these are the preferred preparations to use. Recent recommendations providing acellular pertussis in the routine use of booster doses of diphtheria–tetanus immunizations (Tdap) to adolescents (>11 years) and adults

Hepatitis A Vaccine

vaccines are made from formalin-inactivated hepatitis A virus and are therefore safe for HIV-infected children and adults. As with other vaccines, however, patients with severe immunosuppression may have a suboptimal response. The need for booster doses has not been determined.

Hepatitis B Vaccine

in HIVinfected children, the antibody response mounted against HBV does not appear to be long lasting. For infants, two schedules are available. One is recommended in countries where perinatal transmission of HBV is frequent (birth, 6 weeks, 10 weeks, 14 weeks) and a second can be used where perinatal transmission is less frequent (6 weeks, 10 weeks, 14 weeks). For older children and adults, three doses would also be required (0, 1-2 months, 4-6 months)

Haemophilus influenzae, Type B Vaccine

The HIB vaccine can be provided to asymptomatic or symptomatic HIV-infected children. Infants and children who are severely immunocompromised may not respond to the vaccine as well as those children who are immunocompetent.

Human Papillomavirus Vaccine

There are currently no data available on the immunogenicity, safety, and efficacy of the HPV vaccine in HIV-infected persons. But because the HPV vaccine is a noninfectious vaccine, one can administer it to HIV-infected (asymptomatic or symptomatic) women. However, the immune response might be less vigorous in those individuals who are severely immunocompromised.

Measles Vaccine

IV-infected children have an increased risk of developing severe complications when infected with measles. A review of reported cases of measles infections in children with HIV indicates a 40% death rate. The WHO recommends that HIV-infected children be offered measles vaccination as soon as possible. Therefore, children who are HIV infected can receive measles vaccine at 6 months of age, followed by a second dose at 9 months of age.

Polio Vaccine

WHO continues to recommend the use of OPV in infants and children with an unknown HIV status or for those HIV-infected children who are asymptomatic in resource-limited areas. Symptomatic HIV-infected children can receive the IPV. OPV is administered by mouth. IPV is administered via subcutaneous injection in the upper arm or thigh. There are no immediate side effects secondary to OPV administration. Vaccine-associated paralytic polio usually occurs within 2 months after immunization, but the risk is low, estimated at 1:7.8 million doses

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