Medically reviewed by Biljana Srbinovska, MPharm. Last reviewed July 2026.
Before a vaccine reaches the public in the US, it passes through laboratory testing, three phases of human trials involving tens of thousands of people, a full FDA review of both the product and the factory that makes it, and ongoing safety monitoring afterwards. Full approval, called a Biologics License Application, sets a higher evidence bar than an Emergency Use Authorization, which can only be used during a declared emergency. One thing to know up front: US vaccine policy went through significant institutional change and litigation during 2025 and 2026, so for the current recommendation on any specific vaccine, check the CDC schedule directly and note its revision date. Here is how the process works.
The Stages, Start to Finish
| Stage | What happens | Typical size |
|---|---|---|
| Preclinical | Laboratory and animal studies for safety and immune response | No human subjects |
| IND application | Sponsor files to begin human trials; FDA has 30 days to object | — |
| Phase 1 | Safety, dosing, immune response | 20 to 100 healthy adults |
| Phase 2 | Safety, immune response, schedule | Several hundred |
| Phase 3 | Efficacy against disease, plus rarer side effects | Thousands to tens of thousands |
| BLA review | FDA reviews all data plus manufacturing, and inspects the factory | 6 to 10 months |
| Lot release | Each batch tested and released before distribution | Ongoing |
The whole path from laboratory to licence has historically taken 10 to 15 years. The COVID-19 vaccines were compressed to roughly a year by running steps in parallel, reviewing data as it arrived, and funding manufacturing before approval rather than after, not by skipping trial phases.
Approval Versus Emergency Authorization
These are different things with different evidence standards, and the distinction matters.
Full BLA approval requires substantial evidence of effectiveness and demonstrated safety from well-controlled trials, plus proof the product can be made consistently. It results in a permanent licence for both the vaccine and the factory.
Emergency Use Authorization can only be issued during a declared public health emergency. Its standard is that the product “may be effective” and that its known benefits outweigh its known risks, with no adequate approved alternative available. This is a lower bar than approval, and an EUA ends when the emergency declaration ends.
Accelerated approval, which relies on a marker reasonably likely to predict benefit with confirmatory trials required afterwards, is used mainly for drugs and is rare for vaccines.
The Advisory Committee
During review, the FDA may convene the Vaccines and Related Biological Products Advisory Committee, an external panel that reviews the data publicly and votes. The vote is advisory. The FDA is not required to convene the committee for every product and is not bound by its recommendation.
Separately, after a vaccine is licensed, a CDC committee called the Advisory Committee on Immunization Practices recommends how it should be used and who should receive it. This is a different body from the FDA panel, and its recommendations feed the CDC immunization schedule.
Safety Monitoring After Approval
Approval is not the end of oversight. Several systems track vaccines in use.
VAERS, the Vaccine Adverse Event Reporting System, is a passive system that anyone can file a report to, including patients and parents. This is its strength and its limitation. Reports are unverified, do not by themselves establish that a vaccine caused an event, and are used as an early warning to flag things worth investigating. A raw VAERS report is a signal to check, not a proven side effect, and it is frequently misrepresented as the latter.
The Vaccine Safety Datalink uses real health records from participating systems to compare vaccinated and unvaccinated groups, which VAERS cannot do.
The BEST system uses large insurance and health record databases, including Medicare data, for active surveillance.
The FDA can also require further studies as a condition of licensure, such as pregnancy registries or long-term monitoring for rare events.
The Current Institutional Picture
This area changed substantially during 2025 and 2026, and remains subject to litigation, so this section describes the situation in broad terms rather than as settled fact.
There were significant changes to the membership of the CDC’s immunization advisory committee, changes in FDA and CDC leadership including several departures, and revisions to the childhood immunization schedule, some of which moved vaccines from universal recommendation to shared clinical decision-making between patient and clinician. Several of these changes were challenged in court, and in early 2026 a federal court stayed some of them, which shifted which version of the schedule was legally in effect during the year.
Because the position moved more than once, the only reliable way to know the current recommendation for a given vaccine is to check the CDC schedule directly at the time you need it, and to look at the revision date on the page.
Why This Affects Your Insurance
There is a direct practical consequence worth understanding.
Under the Affordable Care Act, most health plans must cover immunizations recommended by the CDC committee with no cost sharing. If a vaccine loses that recommendation, the requirement to cover it without a copay can fall away, and access through the Vaccines for Children program can also be affected.
Some insurers made voluntary commitments to keep covering vaccines recommended as of a particular date, but those are commitments rather than legal guarantees and they have expiry dates.
Access to COVID-19 vaccines in particular has come to vary by state, with some states requiring a prescription and some pharmacies restricting administration. Check your state health department’s guidance and confirm coverage with your own plan before assuming a vaccine is free to you.
FDA Vaccine Approval FAQs
How long does it take to approve a vaccine?
Historically 10 to 15 years from laboratory to licence. The COVID-19 vaccines were compressed to about a year by running steps in parallel and pre-funding manufacturing, not by skipping trials.
Full approval requires substantial evidence of effectiveness and safety from controlled trials and grants a permanent licence. An Emergency Use Authorization can only be issued during a declared emergency, uses a lower “may be effective” standard, and ends when the emergency ends.
What is VAERS, and does a report mean a vaccine caused harm?
VAERS is a reporting system anyone can file to. A report is unverified and does not establish that a vaccine caused the event. It is an early warning used to flag issues for investigation, not proof of a side effect.
How many people are in a vaccine trial?
Phase 1 involves 20 to 100 people, phase 2 several hundred, and phase 3 typically thousands to tens of thousands, which is where efficacy and less common side effects are assessed.
How do I find the current vaccine recommendations?
Check the CDC immunization schedule directly and note its revision date. US vaccine policy changed and was litigated during 2025 and 2026, so recommendations should be confirmed at the time you need them rather than relied on from older articles.
Does losing a recommendation affect insurance coverage?
It can. Plans must cover CDC-recommended immunizations without cost sharing, so if a vaccine loses that recommendation the no-copay requirement can end. Confirm coverage with your plan.
