The United States, for instance, conducted a study of the efficiency of a mono-dose of anti-varicella vaccination and found out that this was decreased, since epidemics were created, with the sole benefit of the children suffering from lighter forms of the illness. In light of these findings then, the recommendation was that of administering a second dose (Lopez, Guris, Zimmerman, Gladden, Moore, Haselow, Loparev, Schmid, Jumaan and Snow, 2006)
In spite of vaccination enhancements, incidences of pertussis have been rising. Recent outbreaks of pertussis have been linked to changes in the vaccine ingredients, leading to less effective protection (Geggel, 2015)