What Would Happen If Too Many People Stopped Vaccinating?

This is a popular question presented by those who push for mandatory vaccination. It is also a concern for families with an immunocompromised child. Currently in the United States, most vaccine-preventable diseases are at an all-time low. But is that only because most people vaccinate? If too many stopped vaccinating, let’s say 25% or even 50%, would diseases return? And if diseases increased significantly, what would the fatality and complication rate in our country be?

Diseases that would NOT increase

Let’s first look at the ones which would not increase if there was a widespread decrease in vaccination:

Four of the 16 vaccine-preventable diseases are not communicable through casual person-to-person contact; therefore, lower vaccination rates cannot put vaccinated or immunocompromised people at any increased risk:

  1. Tetanus is not contagious at all
  2. Hepatitis B only spreads through sexual contact, the sharing of IV drug needles, or mixing of infected blood, not casual contact
  3. HPV also spreads only through sexual contact, and therefore is not communicable in a casual manner
  4. Meningococcus (meningitis) is carried asymptomatically in the nasal passages of about 1 in 10 people; it is often a person’s own germ which flares up into symptomatic infection. And once sick, it doesn’t spread through casual contact


Five of the 16 vaccines only protect the individual receiving the vaccine; they do not keep the disease from spreading to other people:

  1. Polio: the injected polio vaccine only prevents internal neurological symptoms in the person who is vaccinated, it does not prevent the transmission of the disease in the population
  2. Pertussis: the acellular pertussis vaccine may help prevent individual cases during young childhood, but wears off quickly and does not prevent transmission of the disease within the population; for example, in 2014, 90% of California children who caught pertussis were already vaccinated
  3. Flu: the influenza vaccine does not prevent wide-spread yearly circulation of the flu; the vaccine can only provide limited individual protection
  4. Diphtheria: the diphtheria vaccine prevents the disease toxin from causing individual disease, it does not prevent germ transmission from person to person
  5. Tetanus: this vaccine only protects the individual who receives it


Three of the 16 diseases have so many strains that vaccination does little to reduce the prevalence of the disease; in fact, it increases other strains not covered by the vaccine:

  1. Pneumococcus: there are more than 80 strains of pneumococcal bacteria, and the vaccine only contains 13 strains
  2. Flu: several different strains of influenza circulate every year, and the vaccine only covers a few of them. Since the vaccine is based on an estimation months in advance, it often fails to match the strains that do circulate
  3. HPV: there are about 100 strains of HPV, and the vaccine only protects against 2, 4, or 9, depending on the brand


While vaccines for the above diseases may reduce the chance of an individual catching a disease if exposed, a decline in vaccination rates would not result in an increase spread of these nine diseases to vaccinated or immunocompromised people.


Diseases that might increase, but are generally mild in virtually all cases


Vaccines have helped lower the prevalence of certain common childhood diseases and can prevent symptoms in some individuals who receive them. The incidence of these particular diseases might increase if vaccination rates declined significantly, but just how deadly would these diseases be in the United States? Looking back at the fatality and complication rates before vaccines were introduced gives us a picture of what we could expect:



In the several years preceding the introduction of measles vaccine in 1963, almost every child caught measles and developed lifetime immunity. The death rate from measles in the U.S. in the 1950’s and early 1960’s was 1 in 500,000 people in the population. Out of those who caught the illness, the fatality rate was 1 death in every 10,000 cases. (Today, the media often report a falsely elevated fatality rate of 1 in 500 cases. Such fatality rates are calculated by the CDC using only reported cases of measles that are severe enough to seek medical care during limited outbreaks, not the total actual cases in a population.)



Prior to the vaccine in 1967, about 1 in 1000 people caught mumps and acquired lifetime immunity, and fatalities were rare: about 1 in every 5000 reported cases. Like measles, most cases were so mild they went unreported. Complications like infertility in adult males and hearing loss were also uncommon (1 in 7700 and 1 in 20,000 of those who caught the disease). In the population as a whole, 1 in almost 4 million people died from mumps.



Widespread use of the rubella vaccine began in 1969. At that time, the fatality rate from this relatively harmless illness was 1 person per 9 million in the population. The reason for the vaccine is that in pregnant women who caught the disease, the infection caused birth defects in about 1 in 20,000 births.


Chicken pox

Like measles, almost every child would catch chicken pox, and the fatality rate was about 1 in every 60,000 cases. In the population as a whole, 1 in 2.3 million Americans died of complications from chicken pox every year. Introduction of the vaccine in 1995 has helped reduce the illness, but it remains harmless for virtually every child who does catch it.


Hib disease

Before the vaccine for Hib was introduced in 1985, about one in 2 million people in the U.S. population died annually from this illness. Including permanent harm from the meningitis disease, like brain damage or deafness, this risk was about 1 in 600,000 in the population.



This mild illness had an extremely low death rate prior to the vaccine being introduced in 2006 (about 1 in 10 million in the U.S. population).



Even though the injected polio vaccine does not prevent transmission between people (see above), and the illness therefore would not increase if more people opted out of the vaccine, it is useful to know the statistics of this disease to understand what could happen if it did return. Before widespread use of the vaccine in 1955, the fatality or permanent paralysis rate from the disease in the U.S. population was 1 in 100,000 people. 95% of people who caught it had no symptoms and 4% had minor fever and upset stomach. Only about 1% suffered neurological complications, and about half of these fully recovered with physical therapy.



There Is NO Risk That Warrants Mandatory Vaccination


So what would actually happen if a significant number of people opted out of certain vaccines? First, more than half of our 16 vaccines don’t even prevent the spread of diseases through every-day casual contact. Second, based on the above data from today and from the pre-vaccine era in the United States, the risk of fatalities and complications IF certain contagious diseases came back is low. To put this into historical perspective, the risk of dying from or being permanently harmed by any of these diseases in the years before vaccines was lower than the risk of being struck by lightning in your lifetime (1 in 12,000). In fact, the flu, an illness which we all deal with every year despite vaccination, actually causes more fatalities than any other vaccine-preventable disease, both now and in the years right before each vaccine was introduced.


Perhaps more importantly, the number of unvaccinated children would have to be significantly high to trigger a resurgence of contagious diseases in our population. Currently, according to the CDC, less than 1% of U.S. children are completely unvaccinated. For this reason, the risk of large disease outbreaks is NOT a realistic threat to Americans. And in the event of an outbreak, instead of mandatory vaccination for everyone, quarantine and targeted vaccination (if necessary) is a more effective, appropriate, and adequate response that safeguards public health.



CDC: Reported Cases and Deaths from Vaccine Preventable Diseases, United States, 1950-2011.

Vital Statistics Rates in the United States 1940-1960 – Online database

California Department of Public Health Statistics, 2014

CDC National Immunization Survey, 2014