Military recruits in basic training receive a series of vaccinations that typically includes adenovirus, hepatitis A, hepatitis B, influenza (when required), measles-mumps-rubella (MMR), meningococcal, polio, tetanus-diphtheria, and varicella. Most of these are given within the first few days of arriving at a reception battalion, often before formal training even begins. The exact combination depends on your existing immunization records, blood test results, and which branch you’re entering.
What Happens During Medical Processing
Vaccinations happen during the reception phase, which is the administrative period before your actual training cycle starts. At most installations, recruits receive their baseline vaccinations and blood draws on Day 1 of processing. On Day 3, they return for a tuberculosis skin test reading and any additional vaccinations flagged by their blood work. If your blood tests show you already have immunity to a particular disease (from childhood vaccines, for example), you may skip that shot. If your titers come back low, you’ll get the vaccine.
This means the bulk of your shots happen in a short window. Expect to move through a line where multiple injections are administered quickly, sometimes several in one visit. Soreness in both arms is normal for a day or two afterward.
The Standard Vaccine Lineup
While the exact list is governed by a joint military regulation (AR 40-562) and can be updated, here’s what recruits have historically received:
- Adenovirus Types 4 and 7: This is an oral vaccine (a pill, not a shot) approved for military personnel ages 17 through 50. The Department of Defense recommends it specifically for recruits entering basic training because adenovirus spreads easily in crowded barracks and causes respiratory illness that can sideline entire platoons.
- Hepatitis A: A two-dose series protecting against a liver infection spread through contaminated food or water, relevant for deployments overseas.
- Hepatitis B: A multi-dose series for a bloodborne liver infection. If you didn’t complete this series as a child, you’ll start or continue it in basic.
- Measles, Mumps, and Rubella (MMR): Given if blood work shows insufficient immunity, even if you were vaccinated as a kid.
- Meningococcal: Protects against bacterial meningitis, which can spread rapidly in group living environments like barracks.
- Polio (IPV): A booster if your records or blood work indicate you need one.
- Tetanus-Diphtheria: A booster to keep protection current, typically given if it’s been more than a few years since your last dose.
- Varicella: The chickenpox vaccine, given if you lack documented immunity.
Not every recruit gets every shot on the list. Your blood titers determine which ones you actually need. Someone who had a complete childhood vaccination schedule and still shows strong immunity might receive fewer injections than someone whose records are incomplete or whose immunity has waned.
The “Peanut Butter Shot”
The most talked-about injection in basic training isn’t technically a vaccine. It’s a large dose of bicillin, a thick, long-acting form of penicillin injected into the buttock. Recruits call it the “peanut butter shot” because of its dense, paste-like consistency, which makes the injection noticeably uncomfortable and leaves the muscle sore for days.
The purpose is preventive. When hundreds of recruits from across the country are packed into barracks, upper respiratory infections (particularly strep throat) spread fast. This single injection of penicillin provides weeks of antibiotic protection during the vulnerable early period when everyone’s immune system is adjusting to close quarters, stress, and sleep deprivation. The soreness is real, and sitting down comfortably can be a challenge for a couple of days, but it’s a straightforward part of the process that virtually every recruit goes through.
If you have a documented penicillin allergy, let your medical team know. You’ll receive an alternative antibiotic instead.
Flu and COVID-19 Shots
These two vaccines have seen significant policy shifts in recent years. The COVID-19 vaccine mandate was dropped by the Pentagon in January 2023 after Congress moved to rescind it. As of April 2025, Defense Secretary Pete Hegseth announced that annual flu vaccination is also no longer required for all troops, citing medical autonomy and religious freedom. His directive does allow individual service branches to request to keep the flu vaccine requirement in place, so the policy may vary depending on your branch and when you ship out.
In practical terms, you may still be offered both vaccines during reception, but they are not mandatory in the way the core vaccines listed above are.
How Exemptions Work
Medical exemptions are possible but require documentation. Your healthcare provider determines whether an exemption is appropriate based on your health and the specific vaccine in question. Medical exemptions can be temporary (lasting up to 365 days) or permanent, and they’re typically granted when an underlying health condition makes a particular vaccine risky for you.
Religious and administrative exemptions also exist within the military system, though the approval process varies by branch and can take time. If you have a known allergy or medical condition that affects vaccination, bring documentation from your civilian doctor. It won’t guarantee an exemption, but it gives the military medical staff the information they need to evaluate your situation quickly during the fast-paced reception process.
What to Bring and How to Prepare
Bring your civilian immunization records if you have them. Shot records from your pediatrician, school, or state immunization registry can save you from getting vaccines you don’t need. Without records, the military defaults to vaccinating you, since it’s safer to re-administer most vaccines than to leave a gap in protection.
There’s no real way to physically prepare for the shots themselves. Stay hydrated, don’t tense up during injections, and expect some arm soreness. The peanut butter shot in the glute will likely be the most uncomfortable, but the soreness fades within a few days. You’ll be doing physical training through all of it, which most recruits say actually helps work out the stiffness faster.