Editing Vaccination (section)

=== Vaccine development and approval ===
Just like any medication or procedure, no vaccine can be 100% safe or effective for everyone because each person's body can react differently.<ref>{{Cite web|url=https://www.cdc.gov/vaccinesafety/ensuringsafety/history/index.html|title=History of Vaccine Safety History Ensuring Safety Vaccine Safety CDC|date=10 January 2019|website=U.S. [[Centers for Disease Control and Prevention]] (CDC)|access-date=12 March 2019|archive-date=28 March 2019|archive-url=https://web.archive.org/web/20190328070048/https://www.cdc.gov/vaccinesafety/ensuringsafety/history/index.html|url-status=live}}</ref><ref name="Chen-1998">{{cite journal | vauthors = Chen RT, Hibbs B | s2cid = 13364842 | title = Vaccine safety: current and future challenges | journal = Pediatric Annals | volume = 27 | issue = 7 | pages = 445–55 | date = July 1998 | pmid = 9677616 | doi = 10.3928/0090-4481-19980701-11 }}</ref> While minor [[side effect]]s, such as soreness or low grade fever, are relatively common, serious side effects are very rare and occur in about 1 out of every 100,000 vaccinations and typically involve [[Allergy|allergic reactions]] that can cause hives or difficulty breathing.<ref name="NIH-site-2019">{{Cite web|url=https://www.niaid.nih.gov/research/making-safe-vaccines|title=Making Safe Vaccines NIH: National Institute of Allergy and Infectious Diseases|website=www.niaid.nih.gov|access-date=12 March 2019|archive-date=28 March 2019|archive-url=https://web.archive.org/web/20190328065701/https://www.niaid.nih.gov/research/making-safe-vaccines|url-status=live}}</ref><ref name="USCDC-2018">{{Cite web|url=https://www.cdc.gov/vaccines/vac-gen/side-effects.htm|title=Vaccines: Vac-Gen/Side Effects|date=12 July 2018|website=U.S. [[Centers for Disease Control and Prevention]] (CDC)|access-date=12 March 2019|archive-date=17 March 2017|archive-url=https://web.archive.org/web/20170317050028/https://www.cdc.gov/vaccines/vac-gen/side-effects.htm|url-status=live}}</ref>

However, vaccines are the safest they ever have been in history and each vaccine undergoes rigorous clinical trials to ensure their safety and [[Vaccine efficacy|efficacy]] before approval by authorities such as the US [[Food and Drug Administration]] (FDA).<ref name="USCDC-2018b">{{Cite web|url=https://www.cdc.gov/vaccinesafety/ensuringsafety/index.html|title=Ensuring Vaccine Safety Ensuring Safety Vaccine Safety CDC|date=12 December 2018|website=U.S. [[Centers for Disease Control and Prevention]] (CDC)|access-date=12 March 2019|archive-date=12 March 2019|archive-url=https://web.archive.org/web/20190312165811/https://www.cdc.gov/vaccinesafety/ensuringsafety/index.html|url-status=live}}</ref>

Prior to human testing, vaccines are tested on [[cell culture]]s and the results modelled to assess how they will interact with the immune system.<ref name="NIH-site-2019" /><ref name="USCDC-2018b" /> During the next round of testing, researchers study vaccines in animals, including [[Mouse|mice]], [[rabbit]]s, [[guinea pig]]s, and [[monkey]]s.<ref name="NIH-site-2019" /> Vaccines that pass each of these stages of testing are then approved by the public health safety authority (FDA in the United States) to start a three-phase series of human testing, advancing to higher phases only if they are deemed safe and effective at the previous phase. The people in these trials participate voluntarily and are required to prove they understand the purpose of the study and the potential risks.<ref name="USCDC-2018b" />

During phase I trials, a vaccine is tested in a group of about 20 people with the primary goal of assessing the vaccine's safety.<ref name="NIH-site-2019" /> Phase II trials expand the testing to include 50 to several hundred people. During this stage, the vaccine's safety continues to be evaluated and researchers also gather data on the effectiveness and the ideal dose of the vaccine.<ref name="NIH-site-2019" /> Vaccines determined to be safe and efficacious then advance to phase III trials, which focuses on the efficacy of the vaccine in hundreds to thousands of volunteers. This phase can take several years to complete and researchers use this opportunity to compare the vaccinated volunteers to those who have not been vaccinated to highlight any true reactions to the vaccine that occur.<ref name="USCDC-2018b" />

If a vaccine passes all of the phases of testing, the manufacturer can then apply for license of the vaccine through the relevant regulatory authorities such as the FDA in US. Before regulatory authorities approve use in the general public, they extensively review the results of the clinical trials, safety tests, purity tests, and manufacturing methods and establish that the manufacturer itself is up to government standards in many other areas.<ref name="NIH-site-2019" /><ref name=":who_vac_dev">{{Cite press release |url=https://www.who.int/news-room/feature-stories/detail/how-are-vaccines-developed|title=How are vaccines developed? WHO|date=8 December 2020|website=[[World Health Organization]] (WHO)|access-date=26 October 2023|archive-date=26 October 2023|archive-url=https://web.archive.org/web/20231026062500/https://www.who.int/news-room/feature-stories/detail/how-are-vaccines-developed|url-status=live}}</ref>

After regulatory approval, the regulators continue to monitor the manufacturing protocols, batch purity, and the manufacturing facility itself. Additionally, vaccines also undergo phase IV trials, which monitor the safety and efficacy of vaccines in tens of thousands of people, or more, across many years.<ref name="NIH-site-2019" /><ref name=":who_vac_dev" />