23 October 2017

Take 5: How are polysaccharide and conjugate vaccinations different?

Clinical Immunology

The difference between the older, first-generation meningococcal vaccine and new, conjugate vaccine is the makeup.

Both the polysaccharide vaccine and the conjugate vaccine protect against four strains of meningococcal: A, C, W and Y.

The conjugate vaccine, which has now replaced the polysaccharide vaccine, is constructed differently, says Associate Professor Kristine Macartney, a paediatric infectious disease specialist.

In the polysaccharide vaccine, only the sugar part of the bacteria, the capsule, is included as the antigen to stimulate the immune response.

“In the conjugate vaccine, it’s actually the sugar joined to the carrier protein,” says Associate Professor Kristine Macartney.

“The carrier protein means that it tickles another part of the immune system, which indeed provokes a stronger response and has the advantage of also giving immunologic memory so we can give more doses and boosting effects, so additive effects.

“And, in addition, we know that conjugate vaccine has enough protection that then you can reduce the likelihood of carriage of bacteria in the nose.”