How Vaccines Get FDA Approved: CBER, VRBPAC, ACIP

Most biotech investors know what a PDUFA date is. Few know that vaccines follow a different FDA regulatory path than drugs, that a second gate called ACIP can kill a commercially approved product, and that vaccine efficacy numbers measure something fundamentally different from therapeutic endpoints. Here is how to read the vaccine approval process as an investor.

The one-sentence answer: Vaccines go through a different FDA center, a different advisory committee, and a second commercial gate at the CDC, so the binary risk is not just at the PDUFA date but at the ACIP recommendation that follows it.

Step 1: Know which FDA center reviews the vaccine

The FDA has two centers that review human therapeutics. CDER (Center for Drug Evaluation and Research) reviews small molecule drugs and most biologics. CBER (Center for Biologics Evaluation and Research) reviews vaccines, blood products, and cell and gene therapies.

Why this matters for investors: different review teams, different internal standards, different advisory committees. A drug PDUFA and a vaccine PDUFA are not the same event even though the deadline mechanism is identical. CBER reviewers are comfortable with the immune-response correlates and large prophylactic trial designs that vaccine applications require. CDER reviewers are not, because they rarely see them.

The practical implication: when a vaccine company files a BLA, the review happens at CBER. When a small molecule or monoclonal antibody company files an NDA or BLA, the review typically happens at CDER. The center assignment is not random, it is determined by product type under the FDA intercenter agreement.

Step 2: Read the BLA trial design

Vaccines are reviewed under the BLA (Biologics License Application) pathway, the same application type used for monoclonal antibodies and gene therapies. The difference is the trial design.

Prophylactic vaccines must demonstrate efficacy in preventing disease, not treating it. That means Phase 3 trials enroll tens of thousands of healthy volunteers, not hundreds of sick patients. The COVID vaccine trials enrolled 30,000 to 45,000 participants each. A therapeutic cancer drug Phase 3 typically enrolls 300 to 1,000 patients.

The endpoint is usually a reduction in infection rate compared to placebo, or an immune response correlate that predicts protection. A vaccine efficacy (VE) of 60% means the vaccine reduced infections by 60% relative to the placebo group. That number is a relative risk reduction, not an absolute risk reduction, and the distinction matters: a 60% RRR against a 2% baseline infection rate is a 1.2% absolute risk reduction. Companies almost always quote the RRR because it sounds better. Read both.

Step 3: Understand the VRBPAC advisory committee

Vaccines get their own advisory committee: VRBPAC (Vaccines and Related Biological Products Advisory Committee), separate from ODAC (oncology) or the other drug committees. VRBPAC votes on whether the vaccine’s benefits outweigh its risks, and the FDA typically follows the vote.

The Moderna (MRNA) flu vaccine mRNA-1010 (mFLUSIVA) is the 2026 example. The FDA initially refused to file the application earlier this year, citing comparator concerns. Moderna resubmitted, and on June 18, 2026, VRBPAC voted unanimously 9-0 in favor of approval for adults 50 and older, with a PDUFA date of August 5, 2026. A unanimous AdCom vote is a strong positive signal: the FDA agrees with roughly 97% of yes votes. But the earlier refusal-to-file shows that VRBPAC scrutiny can swing the outcome well before the vote happens.

For more on how AdCom votes work and why they matter, see the FDA AdCom explainer.

Step 4: Wait for the ACIP recommendation

This is the second gate, and it is the one most drug investors miss.

After the FDA approves a vaccine, the CDC’s ACIP (Advisory Committee on Immunization Practices) votes on whether to recommend the vaccine for specific populations. Private insurers, Medicare Part D, and Medicaid are generally required to cover vaccines that carry an ACIP recommendation. Without the recommendation, insurance coverage is inconsistent and the commercial market shrinks dramatically.

A vaccine can be FDA-approved and commercially dead without ACIP. This is not theoretical: vaccines that receive a “shared clinical decision-making” recommendation, the weakest ACIP category, see meaningfully lower uptake than vaccines with a “routine” recommendation. The ACIP recommendation categories directly shape demand.

The investor takeaway: an FDA approval pop on a vaccine stock can fade fast if ACIP gives a narrow or weak recommendation. Do not model peak sales until ACIP has voted.

Step 5: Read vaccine efficacy as relative risk reduction

Vaccine efficacy (VE) is calculated as 1 minus the relative risk. If the placebo group has a 10% infection rate and the vaccine group has a 4% infection rate, the relative risk is 0.4, and the VE is 60%.

Companies quote the RRR because it sounds impressive. The absolute risk reduction (ARR) is the difference between the two rates, which is 6% in the example above. The number needed to treat (NNT) is 1 divided by the ARR, so roughly 17 people need to be vaccinated to prevent one infection.

Seasonal flu vaccine efficacy varies year to year because the circulating strain changes. A flu vaccine that is 60% effective in a well-matched year can be 20% effective in a poorly matched year. Read the trial data against the circulating strain, not against a multi-year average. For a deeper look at the Moderna flu vaccine PDUFA and the data behind it, see the mRNA-1010 analysis.

Step 6: Watch post-approval surveillance

Vaccines are given to healthy people, often millions of them, so safety signals carry outsized weight. The VAERS (Vaccine Adverse Event Reporting System) database collects reports after approval, and Phase 4 commitments can require additional safety studies.

The cautionary example is RotaShield, the first rotavirus vaccine, approved in 1998 and withdrawn within roughly a year after VAERS data showed an increased risk of intussusception (a bowel obstruction) in the week after the first dose. The product was pulled from the US market. A vaccine approval is not permanent; a safety signal can end the commercial run.

Common mistakes

Assuming FDA approval equals revenue. For drugs, approval is the finish line. For vaccines, approval is the halfway point. ACIP determines whether the product reaches the commercial market. Modeling peak sales before the ACIP vote is a common error.

Confusing vaccine efficacy with absolute risk reduction. A 90% VE sounds like a sure thing. If the baseline infection risk is 1%, the absolute benefit is 0.9 percentage points. Read both numbers before estimating market penetration.

Treating a vaccine PDUFA like a drug PDUFA. The binary risk at the PDUFA date is real, but the second binary at ACIP is the one that moves the commercial trajectory. A positive FDA vote followed by a weak ACIP recommendation can leave the stock flat or down.

Ignoring manufacturing scale. Vaccines are biologics, so manufacturing is harder than small molecules. A company that wins approval but cannot produce enough doses to meet demand will not capture the market. Check capacity before modeling peak sales.

Final checklist

• Identify the reviewing center: CBER for vaccines, CDER for most drugs and biologics.
• Read the BLA trial design: prophylactic vaccines enroll tens of thousands; efficacy is measured as relative risk reduction.
• Track the VRBPAC vote: a positive vote is a strong signal, but the FDA follows it roughly 97% of the time, not 100%.
• Wait for the ACIP recommendation: the second gate that determines commercial uptake and insurance coverage.
• Read both RRR and ARR: companies quote RRR; the absolute number tells you the real-world impact.
• Watch post-approval surveillance: VAERS and Phase 4 can withdraw an approved product, as RotaShield showed.

For the foundational PDUFA mechanism, see the PDUFA explainer. For the BLA vs NDA distinction, see the application types guide. For the accelerated approval pathway, see the accelerated approval explainer. For the broader infectious disease catalyst calendar, see the 2026 infectious disease ranking.