How do maternal antibodies influence the effectiveness of early-life vaccinations, and what strategies can be used to enhance vaccine response in infants?

Maternal antibodies—primarily IgG antibodies transferred from mother to infant through the placenta during pregnancy—play a crucial role in protecting newborns from infections in early life. However, these same maternal antibodies can influence the effectiveness of early-life vaccinations in several ways:

Influence of Maternal Antibodies on Early-life Vaccinations

Maternal antibodies can bind to the vaccine antigens (especially live attenuated or subunit vaccines), neutralizing them before they stimulate the infant’s immune system. This reduces the vaccine’s ability to induce an effective immune response.

The presence of maternal antibodies can mask epitopes on the vaccine antigen, preventing B cell receptors in the infant from recognizing and responding to them. This can lead to reduced antibody production by the infant.

Some evidence suggests maternal antibodies might also interfere with the induction of T cell responses, though this effect is less well characterized.

Maternal antibodies wane over time, typically disappearing by 6 to 12 months of age. Vaccines given too early may be less effective if maternal antibody levels are still high.

Strategies to Enhance Vaccine Response in Infants

• Delayed Vaccination: Administer vaccines at an age when maternal antibodies have declined sufficiently to minimize interference. For example, some vaccines are scheduled starting at 6 months or later.


• Multiple Doses: Use initial doses to prime the immune system and booster doses later to enhance immunity once maternal antibodies have waned.

• Increasing antigen dose or using adjuvants can help overcome maternal antibody interference by eliciting a stronger immune response.

• Use of non-live vaccines or vaccines that stimulate cellular immunity more robustly may be less affected by maternal antibodies.


• For example, conjugate vaccines (like Hib or pneumococcal conjugate vaccines) are designed to be effective in young infants despite maternal antibodies.

• Vaccinating mothers during pregnancy can boost maternal antibody levels, providing better passive immunity to the infant until the infant’s own vaccination schedule begins. This approach protects infants before they can be vaccinated effectively.

• Mucosal vaccines or intranasal vaccines may induce local immunity less affected by circulating maternal antibodies.

• Vaccines designed to induce strong T cell responses may be less susceptible to inhibition by maternal antibodies.

Summary

Maternal antibodies provide important early protection but can reduce the immunogenicity of early-life vaccines by neutralizing vaccine antigens and inhibiting infant immune responses. To enhance vaccine effectiveness, strategies include optimizing the timing and dosing of vaccines, using more immunogenic formulations, leveraging maternal vaccination, and developing novel vaccine platforms that circumvent maternal antibody interference.