There is another benefit of vaccines that you might not be aware of.
Vaccines are typically very effective, but of course, they aren’t perfect.
Fortunately, even when they don’t work and you do get sick, vaccinated kids will often have milder disease than those who are unvaccinated.
Do Vaccinated Kids Who Get Sick Have Milder Disease?
While no one expects to get a vaccine-preventable disease if they have been vaccinated, it is nice to know that often, you will at least have a milder disease.
“Disease may occur in previously vaccinated individuals. Such breakthroughs are either primary – due to vaccine failure – or secondary. In such cases, the disease is usually milder than in the non-vaccinated.”
Vaccination greatly reduces disease, disability, death and inequity worldwide
Milder mumps and pertussis?
“The number of previous vaccine doses was inversely associated with clinical severity.”
Zamir et al on Characteristics of a large mumps outbreak: Clinical severity, complications and association with vaccination status of mumps outbreak cases
Yes!
And that’s good news for all of the folks concerned about waning immunity with these vaccines.
“A protective effect of vaccination was noted when mean duration of symptoms and hospital stay are analysed, comparing unvaccinated, partially vaccinated and fully vaccinated children. We showed a vaccination dose effect trend, with fully vaccinated children having less-severe RVGE than not vaccinated and partially vaccinated children.”
Justino et al on Clinical Severity and Rotavirus Vaccination among Children Hospitalized for Acute Gastroenteritis in Belém, Northern Brazil
Consider that, in addition to preventing disease:
- two doses of MMR has been found to have a significant preventive effect against mumps complications, including orchitis, meningitis, and encephalitis, and hospitalization for mumps
- two doses of the chickenpox vaccine has been found to be very effective at preventing severe disease, in fact, kids with breakthrough chickenpox often don’t have fever, have fewer than 50 spots, and they go away quicker than kids who are unvaccinated.
- vaccinated kids who get pertussis typically don’t cough as long as those who are unvaccinated
- the rotavirus vaccine series, in addition to protecting most kids from getting rotavirus infections in the first place, protected all of the vaccinated kids from getting severe infections
- the flu vaccine reduces the risk of severe disease, especially if you are hospitalized with the flu
What does this all mean?

It means that vaccines work, even when they don’t work as well as we would like them to!
More On the Severity of Breakthrough Infections
- What Are the Benefits of Vaccines?
- Are the Risks Greater Than the Benefits for Any Vaccines?
- The Benefits and Risks of Delaying Vaccines
- Effectiveness Rates of Vaccines
- What Are the Pro and Con Arguments for Vaccines?
- Study – Protective effect of vaccination against mumps complications, Czech Republic, 2007-2012
- Study – Shift within age-groups of mumps incidence, hospitalizations and severe complications in a highly vaccinated population. Spain, 1998-2014
- Study – Severity of mumps disease is related to MMR vaccination status and viral shedding
- Study – Characteristics of a large mumps outbreak: Clinical severity, complications and association with vaccination status of mumps outbreak cases
- Study – Severe varicella in persons vaccinated with varicella vaccine (breakthrough varicella): a systematic literature review
- Study – Varicella breakthrough infection and effectiveness of 2-dose varicella vaccine in China
- Study – Effectiveness of Prenatal Tetanus, Diphtheria, and Acellular Pertussis Vaccination on Pertussis Severity in Infants
- Study – Safety and efficacy of an attenuated vaccine against severe rotavirus gastroenteritis
- Study – Clinical Severity and Rotavirus Vaccination among Children Hospitalized for Acute Gastroenteritis in Belém, Northern Brazil
- Study – Influenza vaccination is associated with reduced severity of community-acquired pneumonia
- Study – Influenza vaccine effectiveness in preventing influenza-associated intensive care admissions and attenuating severe disease among adults in New Zealand 2012-2015
- CDC – New CDC Study Shows Flu Vaccine Reduces Severe Outcomes in Hospitalized Patients
- WHO – Vaccination greatly reduces disease, disability, death and inequity worldwide
- Another Benefit of Vaccines: Milder Disease
- Fatality Rates Of Small-Pox In The Vaccinated And Unvaccinated
- Vaccine adverse events are rare – vast benefits outweigh small risks
- The benefits of the measles vaccine go beyond just protecting against measles, 2019 edition