Table 3.

Summary of Evidence for the Nonspecific Effect of Vaccines^a

Live Attenuated Vaccine	Nonspecific Effects/Benefit Observed
Oral polio virus	• Reduced days of diarrhea (P = .0025) and fewer episodes of Shigella/EIEC when compared with IPV in male infants [23]
	• Reduction in detection of C. jejuni/coli in all infants [23]
	• Lower admissions due to lower respiratory tract infections in vaccinated children [9]
	• OPV campaigns associated with significant decreases in mortality rate (MRR, 0.75), with additional doses associated with a reduction of 14% in mortality rate [8]
MMR	• Lower admissions due to lower respiratory tract infections in vaccinated children [9]
	• A risk reduction of up to 35% in hospitalization due to infectious diseases in the second year of life in high-income countries [54]
BCG	• Reduction in mortality of 3-fold in neonatal vaccinated boys [55]
	• BCG scar associated with lower mortality for children when compared with those without a scar (MR, 0.45; 95% CI, 0.21–0.96) [56]
	• BCG scar associated with a significant reduction in risk of death from malaria [56]
	• An increase of 10% in BCG index was associated with a mortality reduction of 10.4% in COVID-19 mortality [57]
	• Induces emergency granulopoiesis improving survival in neonatal mice during sepsis [24]
Influenza	• Produces strong innate immune responses to provide indirect protection against RSV [19]
Monovalent measles	• Two doses were associated with an all-cause mortality reduction of 22% when given before DTP vaccine in children 4.5–36 months of age [17]
	• Lower mortality among vaccinated children vs unvaccinated children (HR, 0.76; 95% CI, 0.63–0.91), especially for early vaccinated children [58]
	• Early vaccination was associated with a lower risk of hospital admission, particularly for respiratory infections [59]
Attenuated Bordetella pertussis vaccine (BPZE1)	• In animal studies, protects against inflammation and allergen-driven airway pathology from infections due to Bortedella species, RSV, and influenza [16, 18]

Abbreviations: BCG, Bacillus Calmette-Guérin; COVID-19, coronavirus disease 2019; DTP, diphtheria, tetanus, pertussis; EIEC, enteroinvasive Escherichia coli; HR, hazard ratio; IPV, inactivated polio vaccine; MR, mortality rate; MRR, mortality rate ratio; OPV, oral polio vaccine; RSV, respiratory syncytial virus.

^aThis table is not exhaustive of all available data in the literature for all live attenuated vaccines. It summarizes some of the data available that demonstrate the nonspecific effects of vaccines.