Vaccines Fast Facts
CNN Editorial Research
Here’s a look at information and statistics concerning vaccines in the United States. For vaccines related to coronavirus, see Coronavirus Outbreak Timeline Fast Facts.
The Centers for Disease Control and Prevention (CDC) provides vaccine recommendations by age, as well as by disease.
For more than 100 years, there has been public discord regarding vaccines based on issues like individual rights, religious freedoms, distrust of government and the effects that vaccines may have on the health of children.
Exemptions to vaccines fall into three general categories: medical, religious and philosophical.
As of January 2022, 44 states and the District of Columbia have enacted legislation allowing religious exemptions from vaccines, and 15 states allow philosophical (non-spiritual) exemptions.
1855 – Massachusetts mandates that school children are to be vaccinated (only the smallpox vaccine is available at the time).
February 20, 1905 – In Jacobson v. Massachusetts, the US Supreme Court upholds the State’s right to compel immunizing against smallpox.
November 13, 1922 – The US Supreme Court denies any constitutional violation in Zucht v. King in which Rosalyn Zucht believes that requiring vaccines violates her right to liberty without due process. The High Court opines that city ordinances that require vaccinations for children to attend school are a “discretion required for the protection of the public health.”
1952 – Dr. Jonas Salk and his team develop a vaccine for polio. A nationwide trial leads to the vaccine being declared in 1955 to be safe and effective.
1963 – The first measles vaccine is released.
1983 – A schedule for active immunizations is recommended by the CDC.
March 19, 1992 – Rolling Stone publishes an article by Tom Curtis, “The Origin of AIDS,” which presents a theory that ties HIV/AIDS to polio vaccines. Curtis writes that in the late 1950s, during a vaccination campaign in Africa, at least 325,000 people were immunized with a contaminated polio vaccine. The article alleges that the vaccine may have been contaminated with a monkey virus and is the cause of the human immunodeficiency virus, later known as HIV/AIDS.
August 10, 1993 – Congress passes the Omnibus Budget Reconciliation Act which creates the Vaccines for Children Program, providing qualified children free vaccines.
December 9, 1993 – Rolling Stone publishes an update to the Curtis article, clarifying that his theory was not fact, and Rolling Stone did not mean to suggest there was any scientific proof to support it, and the magazine regrets any damage caused by the article.
1998 – British researcher Andrew Wakefield and 12 other authors publish a paper stating they had evidence that linked the vaccination for Measles, Mumps and Rubella (MMR) to autism. They claim they discovered the measles virus in the digestive systems of autistic children who were given the measles, mumps and rubella (MMR) vaccine. The publication leads to a widespread increase in the number of parents choosing not to vaccinate their children for fear of its link to autism.
2000 – The CDC declares the United States has achieved measles elimination, defined as “the absence of continuous disease transmission for 12 months or more in a specific geographic area.”
2004 – Co-authors of the Wakefield study begin removing their names from the article when they discover Wakefield had been paid by lawyers representing parents who planned to sue vaccine manufacturers.
May 14, 2004 – The Institute of Medicine releases a report “rejecting a causal relationship between the MMR vaccine and autism.”
February 2010 – The Lancet, the British medical journal that published Wakefield’s study, officially retracts the article. Britain also revokes Wakefield’s medical license.
2011 – Investigative reporter Brian Deer writes a series of articles in the BMJ exposing Wakefield’s fraud. The articles state that he used distorted data and falsified medical histories of children that may have led to an unfounded relationship between vaccines and the development of autism.
2011 – The US Public Health Service finds that 63% of parents who refuse and delay vaccines do so for fear their children could have serious side effects.
2014 – The CDC reports the number of measles cases at 667.
June 17, 2014 – After analyzing 10 studies, all of which looked at whether there was a link between vaccines and autism and involved a total of over one million children, the University of Sydney publishes a report saying there is no correlation between vaccinations and the development of autism.
December 2014 – A measles outbreak occurs at Disneyland in California.
2015 – In the wake of the theme park outbreak, 189 cases of measles are reported in 24 states and Washington, DC.
February 2015 – Advocacy group Autism Speaks releases a statement, “Over the last two decades, extensive research has asked whether there is any link between childhood vaccinations and autism. The results of this research are clear: Vaccines do not cause autism. We urge that all children be fully vaccinated.”
May 28, 2015 – Vermont Gov. Peter Shumlin signs a bill removing the philosophical exemption from the state’s vaccination law. Parents may still request exemptions for medical or religious reasons. The law goes into effect on July 1, 2016.
June 30, 2015 – California Gov. Jerry Brown signs legislation closing the “vaccine exemption loophole,” by eliminating any personal or religious exemptions for immunizing children who attend school. The law takes effect on July 1, 2016.
January 10, 2017 – Notable vaccine skeptic Robert F. Kennedy Jr. meets with President-elect Donald Trump. Afterwards, Kennedy tells reporters he agreed to chair a commission on “vaccination safety and scientific integrity.” A Trump spokeswoman later says that no decision has been made about setting up a commission on autism.
August 23, 2018 – A study published in the American Journal of Public Health finds that Twitter accounts run by automated bots and Russian trolls masqueraded as legitimate users engaging in online vaccine debates. The bots and trolls posted a variety of anti-, pro- and neutral tweets and directly confronted vaccine skeptics, which “legitimize” the vaccine debate, according to the researchers.
October 11, 2018 – Two reports published by the CDC find that vaccine exemption rates and the percentage of unvaccinated children are on the rise.
2019 – The CDC confirms 1,282 individual cases of measles in 31 states.
January 2019 – The World Health Organization names vaccine hesitancy as one of 10 threats to global health in 2019.
March 26, 2019 – Rockland County, New York announces the “extremely unusual” step of banning unvaccinated individuals under age 18 from public places. One week later, a judge puts a hold on that and prohibits the county from enforcing the ban.
May 10, 2019 – Washington Gov. Jay Inslee signs legislation removing the philosophical exemption for the MMR vaccine from the state’s school immunization requirements.
May 24, 2019 – Maine Gov. Janet Mills signs a bill into law removing all non-medical exemptions to vaccinations. The law will take effect in September 2021, and schoolchildren who claim a non-medical exemption prior to the law taking effect will be allowed to attend school if their parent or guardian provides a written statement from a healthcare professional indicating they’ve been informed of the risks of refusing immunization.
June 13, 2019 – New York Gov. Andrew Cuomo signs legislation that removes nonmedical exemptions from school vaccination requirements. The law goes into effect immediately.
September 4, 2019 – Facebook announces that educational pop-up windows will appear on the social media platforms when a user searches for vaccine-related content, visits vaccine-related Facebook groups and pages, or taps a vaccine-related hashtag on Instagram.
September 9, 2019 – California Democratic Gov. Gavin Newsom signs two bills that limit medical exemptions for vaccines of schoolchildren.
October 4, 2019 – The Department of Health and Human Services announces that the United States has officially maintained its measles elimination status of nearly two decades.
December 19, 2019 – The US Food and Drug administration announces the approval of a vaccine for the prevention of the Ebola virus for the first time in the United States. The vaccine, Ervebo, was developed by Merck and protects against Ebola virus disease caused by Zaire ebolavirus in people 18 and older.
December 27, 2019 – A study published in the medical journal JAMA Network Open finds that a single dose of the human papillomavirus (HPV) vaccine may be just as effective as two or three doses at preventing cancer-causing HPV infection.
February 3, 2020 – The National Institute of Allergy and Infectious Diseases (NIAID) announces that a clinical trial for an HIV vaccine has been discontinued since the vaccine was not found to prevent infections of human immunodeficiency virus, the virus that causes AIDS.
February 17, 2020 – A study published in the medical journal BMJ Case Reports finds that a third of all reported cases of measles have complications such as pneumonia, hepatitis and viral meningitis. The researchers report that anti-vaccination campaigns have contributed to an increase in cases in children and adults. Research shows complications occur most commonly in people under 5 or above 20 years old.
April 28, 2021 – Connecticut Gov. Ned Lamont signs legislation that removes the religious exemption for school vaccinations. The law will go into effect for the 2022-2023 school year.
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