Vaccination of pregnant women against co…

A few reminders on whooping cough and its prevention by vaccination

Whooping cough is a highly contagious infection of the respiratory tract. This disease is serious, sometimes fatal, in infants. There is an effective vaccination, but this cannot be started before the age of 8 weeks; before the age of three months, vaccinated infants are only partially protected by vaccination. In France, more than 90% of pertussis deaths occur in newborns and children under six months. Parents (particularly the mother) and siblings are the main sources of contamination of infants. Vaccination of the entourage (“cocooning”) is a means of protecting them, but this recommendation is not sufficiently applied.

Pertussis vaccines

The list of whooping cough vaccines can be viewed here; the vaccines available in France are all combined with other vaccines, in particular diphtheria and tetanus toxoids, or the vaccine against poliomyelitis, Haemophilus influenzae type b or hepatitis B. A distinction is made between pediatric formulations, containing a full or standard dose of antigen and used in particular for the primary vaccination of infants, and formulations containing a reduced dose of antigen, used for boosters in infants. older children, adolescents and adults, the reduced antigen content allowing to decrease the risk of local inflammatory reaction.

The content of these combination vaccines is represented by valencies designated by the following abbreviations:

  • D: standard dose of diphtheria toxoid;
  • d: reduced dose of diphtheria toxoid;
  • T: tetanus toxoid (regardless of the amount of antigen);
  • P: trivalent vaccine (poliovirus 1, 2 and 3) inactivated against poliomyelitis;
  • Ca: standard dose of acellular pertussis vaccine (as opposed to whole inactivated vaccine, which is no longer used in France at present);
  • ca: reduced dose of acellular pertussis vaccine.

In France, the only formulation available for vaccinating adults (that containing reduced doses of antigen) is quadrivalent, designated by the abbreviation “dTcaP” (diphtheria-tetanus-pertussis-polio). There are two marketed vaccines corresponding to the dTcaP vaccine: the BOOSTRIXTETRA vaccine and the REPEVAX vaccine.

In other European countries and in the United States, there is a trivalent combined form “dTP” or “Tdap” in English (for Tetanus-diphtheria-acellular pertussis), available under several brand names (ADACEL, BOOSTAGEN, BOOSTRIX, COVAXIS, TDAPBOOSTER, TRIAXIS).

New recommendation: vaccination of pregnant women

Published immunogenicity data support a satisfactory immune response in pregnant women. Antipertussis antibodies are transferred to the fetus through the placenta, allowing the newborn and young infant still too young to be vaccinated to be protected.

An inhibitory effect of maternal antibodies on the production of antibodies by the infant’s immune system, called the “blunting” effect, has been described for pertussis and diphtheria vaccines. However, this effect has in practice no impact on the protection against pertussis and diphtheria of subsequently vaccinated children.

Real-life efficacy data from vaccination of pregnant women has confirmed its effectiveness, with a reduction in the number of cases, number of hospitalizations and mortality from pertussis in children aged zero to two months. Compared to vaccination of relatives, vaccination during pregnancy has shown better vaccine efficacy in real life to protect the infant before its own vaccination.

The High Authority for Health (HAS) therefore recommends vaccinate pregnant women against whooping cough from the second trimester of pregnancy, favoring the period between 20 and 36 weeks of amenorrhea (i.e. between the beginning of the 5and month and the end of the 8and month of pregnancy). This strategy makes it possible to increase the passive transplacental transfer of maternal antibodies against pertussis and to ensure optimal protection of the newborn.

Pertussis vaccination should be done during each pregnancyin order to ensure that a sufficient quantity of antibodies is transmitted to the future newborn.

The following clarifications are made:

  • Vaccination during pregnancy can be done with a trivalent (dTca) or tetravalent (dTcaP: BOOSTRIXTETRA or REPEVAX) vaccine, depending on availability (trivalent dTca vaccines are not currently available in France);
  • In all cases, a minimum delay of one month must be respected in relation to the last dTP vaccine (REVAXIS);
  • Vaccination against whooping cough can be done at the same time as vaccination against seasonal flu or covid 19; however, while vaccination against whooping cough should preferably be carried out during the second or third trimester of pregnancy, vaccinations against covid 19 and influenza should be carried out as soon as possible during pregnancy;
  • when the mother has been vaccinated during her pregnancy and at least one month has elapsed between vaccination and childbirth, it is no longer necessary to vaccinate those close to the baby.

In the absence of vaccination of pregnant women during pregnancy, vaccination is recommended :

  • For the mother immediately after childbirth (immediate postpartum)before leaving the maternity ward, even if she is breastfeeding, in accordance with the current strategy for cocooning.
  • For those around the newborn (parents, siblings, grandparents and other people likely to be in close and lasting contact with the future infant during its first six months) no later than the birth of the child, in accordance with previous recommendations.

This new recommendation has been integrated into the vaccine decision support system of MesVaccins and the electronic vaccination record (Figure 1).

Figure 1 : Display of personalized vaccination recommendations in the electronic vaccination record of MesVaccins.net for a 28-year-old pregnant woman.

Reference


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