Valency

vaccine valency

Some etymons appear to have greater valency than others when it comes to the formation of portmanteau words.

The rationale behind GSK's buy is that bigger is better, in terms of vaccine valency. It has been shown that including more disease-causing serotypes decreases the incidence of invasive pneumococcal disease. To this end, Pfizer and Merck last year got the nod for 20-valent and 15-valent vaccines respectively. Affinivax's AFX3772, meanwhile, is a 24-valent jab.