What Shots Do You Get in Basic Training?

New military recruits in the United States typically receive a battery of six to ten or more immunizations during their first few days of basic training, covering everything from routine childhood catch-ups like measles, mumps, and rubella to military-specific vaccines like the adenovirus pill. The exact list depends on your immunization history, the branch of service, and the time of year you ship out, but the core lineup has been remarkably consistent across all branches for decades. What catches most people off guard is not any single vaccine but the sheer volume: multiple injections in both arms, sometimes in the same sitting, plus an oral tablet, and an infamous antibiotic shot that is not technically a vaccine at all.

The Routine Catch-Up Vaccines

A large portion of what you receive at basic training are the same immunizations recommended for all American adults by the Centers for Disease Control and Prevention. The military simply makes sure every recruit is current, regardless of what records you bring with you. The most common routine vaccines administered at initial entry include:

MMR: Measles, mumps, and rubella. You receive this if you cannot document two prior doses or adequate blood titers.
Varicella: The chickenpox vaccine, given if you lack evidence of immunity (either two doses or a documented history of the disease).
Tdap: Tetanus, diphtheria, and pertussis (whooping cough), a single booster shot.
Influenza: A seasonal flu shot, given regardless of whether you received one that year. The military evaluates flu vaccine effectiveness at training centers every season.
Hepatitis A: A two-dose series to protect against a virus spread through contaminated food and water.
Hepatitis B: Historically a three-dose series, though newer two-dose formulations are now in use across some branches.

The military does not simply trust that your childhood vaccinations are still working. A study of over 32,000 Air Force recruits found that only about 82% had protective antibody levels for measles, roughly 80% for mumps, and about 82% for rubella, all below the thresholds generally considered necessary for herd immunity in a close-quarters population.¹ That gap is why you will almost certainly get an MMR booster even if you swear you had one as a kid. Varicella immunity among recruits has also been actively monitored, with large retrospective studies tracking how well childhood vaccination holds up compared to natural chickenpox infection years later.²

The Adenovirus Pill

This is the one vaccine unique to military recruits and virtually unknown to civilians. Adenovirus types 4 and 7 cause febrile respiratory illness that spreads explosively in barracks settings. Symptoms resemble a severe cold or flu, but adenovirus can escalate to pneumonia and, in rare cases, death. The vaccine is an oral tablet, not an injection, which makes it a mild relief on a day otherwise full of needles.

The military originally used highly effective oral adenovirus vaccines for about 25 years, but the sole manufacturer stopped producing them in the mid-1990s, and existing supplies ran out by early 1999.³ What followed was a decade-long stretch during which adenovirus tore through training installations. Hospitalization rates climbed and recruits lost training days by the thousands. When a new manufacturer finally resumed production and the military reintroduced the vaccine in late 2011, the results were dramatic: adenovirus disease burden among trainees dropped roughly a hundredfold, from about 5.8 cases per 1,000 person-weeks down to 0.02.⁴ Researchers estimated the vaccines now prevent roughly one death, well over a thousand hospitalizations, and about 13,000 febrile adenovirus cases among trainees each year.⁴

Even with the vaccine widely available again, outbreaks can still occur if administration is delayed. A study at a Marine Corps training center found that adenovirus remains a serious threat if recruits are not vaccinated promptly upon arrival.⁵ The virus spreads so quickly in shared sleeping quarters that even a few unvaccinated days at the start of training can be enough to spark an outbreak.

The Meningococcal Vaccine

Meningococcal disease, a bacterial infection that can cause meningitis and bloodstream infections, is another particular concern for military populations. The bacteria thrive in the same conditions recruits face: close physical contact, shared sleeping areas, physical stress, and sleep deprivation. In 2006, the Department of Defense switched from the older polysaccharide meningococcal vaccine to the newer conjugate version for all incoming recruits. Over the following years, the incidence of invasive meningococcal disease among active-duty personnel fell from about 0.77 cases per 100,000 person-years down to roughly 0.22.⁶ The conjugate vaccine generates a stronger and longer-lasting immune response than the older version, which made it particularly well suited for young adults entering high-risk congregate settings.

The Bicillin “Peanut Butter Shot”

Ask anyone who has been through basic training what they remember most from the medical processing line, and the answer is almost always the same: the peanut butter shot. Officially, this is an intramuscular injection of bicillin, a thick, long-acting form of penicillin. It is not a vaccine. It is a prophylactic antibiotic designed to prevent streptococcal infections, particularly strep throat and its potentially serious complications like rheumatic fever, which can sweep through groups of young people sleeping in the same room.

The nickname comes from the thick, viscous consistency of the medication and the soreness it leaves behind. Bicillin is injected deep into the gluteal muscle, and because the suspension is so dense, it does not absorb quickly. The injection site can ache and feel like a hard knot for days. Many recruits describe it as the single most painful moment of medical in-processing, which is saying something on a day that involves half a dozen other needles. You may notice some recruits limping for a day or two afterward, particularly those who tense up during the injection rather than relaxing the muscle.

If you have a documented penicillin allergy, you will not receive bicillin. You will typically be given an alternative antibiotic, often in oral form, to cover the same streptococcal risk.

Why the Military Vaccinates So Aggressively

The pace and scale of military immunization can feel overwhelming when you are on the receiving end, but the reasoning is straightforward. Basic training concentrates thousands of young adults from all over the country into a single barracks with shared bathrooms, dining facilities, and sleeping quarters. They are under extreme physical and mental stress, sleeping less than they are accustomed to, and in many cases their immune systems are encountering regional pathogens they have never been exposed to before. This environment is essentially a laboratory for respiratory and droplet-spread disease.

The U.S. military has over two centuries of experience with infectious disease outbreaks during training, and its vaccination program reflects hard lessons learned from those outbreaks. Military researchers have been involved in the invention, development, or improvement of vaccines against more than 20 diseases over that history.⁷ The goal is not just individual protection. When even a small fraction of a training platoon gets sick, it disrupts the entire training schedule, causes lost days, and costs the military real money. Vaccination is treated as a readiness issue, not just a health one.

The influenza vaccine is a good example of how the military approaches this differently from the civilian world. Flu vaccination at training centers is universal and happens during training regardless of personal preference. Effectiveness is actively studied at multiple installations each season, because a flu outbreak in a basic training company can sideline dozens of recruits simultaneously.⁸

The Hepatitis B Schedule and Newer Options

Hepatitis B has been one of the trickier vaccines to administer in a training environment, because the traditional version requires three doses spaced over six months. Recruits typically get the first dose during basic training, but the second and third doses have to happen later, sometimes at a follow-on school or first duty station. That creates a gap where a service member is not fully protected.

Newer hepatitis B vaccine formulations have changed this picture. A modeling study comparing a two-dose adjuvanted hepatitis B vaccine against the traditional three-dose schedule in Marine recruits found that about 92% of those receiving the newer two-dose version were expected to be protected within a month of the second dose, compared to only about 24% of those on the older three-dose schedule at the same point in time.⁹ That gap left roughly three-quarters of Marines on the old schedule unprotected during the five-month wait between the second and third doses. The newer formulation also saved an estimated 17% in costs, largely because fewer recruits needed to be pulled out of training for additional clinic visits.⁹

What Happens If You Already Have Your Shots

Bringing your immunization records to basic training is genuinely useful, and recruiters will often remind you to do so. If your records clearly show that you are up to date on specific vaccines, the medical staff can skip those. In practice, though, documentation gaps are common. Many 18-year-olds do not have easy access to their childhood vaccination records, and the military’s threshold for accepting prior immunization is strict: they want documented proof, not your word that your parents had you vaccinated.

For some vaccines, the military may draw blood and check antibody levels rather than simply re-vaccinating. This is done selectively, not universally, and depends on the vaccine in question and the branch of service. The MMR seroprevalence study mentioned earlier was part of exactly this kind of screening program, using blood draws to determine how many recruits actually had adequate immunity regardless of what their paper records said.¹ The finding that roughly one in five recruits lacked protective levels for measles, mumps, or rubella helps explain why the military often defaults to vaccinating everyone rather than relying on records alone.

If you have already received the adenovirus vaccine during a prior enlistment or at an earlier training program, you will generally not receive it again. But if you have never been through military training, there is essentially no civilian equivalent, so you will be getting it for the first time.

Side Effects and What to Expect Physically

Most recruits experience some combination of sore arms, mild fatigue, and low-grade fever in the 24 to 48 hours after their immunization session. The number of injections amplifies this: when you receive several shots in both arms in the same sitting, it is not unusual to have limited arm mobility for a day or so. Drill instructors generally know this and may adjust physical training slightly on immunization day, though “adjust” in military training is a relative term.

The adenovirus oral vaccine can cause mild gastrointestinal symptoms in some people, since it is a live virus that replicates briefly in the intestinal tract. These symptoms are usually minor and resolve quickly. It is worth knowing that the live adenovirus in the vaccine can be shed in stool for several weeks after administration, but this is not considered a health risk to others in the training environment.

Serious adverse reactions to any of the basic training vaccines are rare, and medical staff are present during and after administration. That said, the simultaneous administration of multiple vaccines occasionally causes more pronounced systemic symptoms, such as a higher fever or greater fatigue, than you might experience getting a single vaccine at your doctor’s office. The military considers this an acceptable tradeoff because the window to vaccinate recruits before they are exposed to close-quarters disease risk is extremely narrow.

Vaccines That Come After Basic Training

The shots you get at basic training are just the beginning. Depending on your military occupational specialty, your deployment orders, and the regions of the world you may be sent to, additional immunizations can follow throughout your career. Some of the more well-known post-basic vaccines include:

Anthrax: A multi-dose series given to service members deploying to certain regions where weaponized anthrax is considered a threat.
Smallpox: Administered via a distinctive bifurcated needle that scratches the skin surface, leaving a characteristic scar. Given to personnel deploying to areas where smallpox could be used as a biological weapon.
Yellow fever: Required for deployment to parts of Africa, Central America, and South America where the disease is endemic.
Japanese encephalitis: Given before deployment to certain parts of Asia and the Western Pacific.
Typhoid: Available as either an injection or an oral series, given for deployments to areas with poor sanitation.

The military’s approach to deployment immunization is guided by the same logic as basic training vaccination: protect the individual, but more importantly, protect the unit’s ability to function. A single case of a preventable tropical disease in a forward-deployed unit can degrade operational capacity in ways that go well beyond one sick person. The U.S. Armed Forces immunization program has historically addressed protection needs based on training risk, occupational exposure, overseas deployment destinations, and underlying health status of individual service members.⁷

Vaccine Refusal and Consequences

Unlike civilian healthcare, where you can generally decline a recommended vaccine, the military treats immunization as a lawful order. Refusing a required vaccine can result in administrative or disciplinary action, up to and including separation from service. The specific consequences depend on the branch, the vaccine in question, and the circumstances, but the bottom line is that if you are joining the military, you are consenting to the immunization program as a condition of service.

There are narrow medical and religious exemption processes, but they are far more restrictive than what most civilians are accustomed to. A medical exemption requires documented proof of a condition that makes a particular vaccine genuinely dangerous for you, such as a severe allergic reaction to a vaccine component. If you are granted an exemption for one vaccine, you still receive all the others. The exemption is specific, not blanket.

The COVID-19 vaccine mandate, which was in effect across all branches from 2021 until it was rescinded by Congress in early 2023, generated significant attention around this topic. But the broader principle of mandatory military immunization predates the COVID-19 era by centuries and remains firmly in place for all the other vaccines described here. The adenovirus vaccine, the meningococcal vaccine, the flu shot, MMR, and the rest are not optional, and there is no indication that will change.

Small Differences Between Branches

The core vaccine list is essentially identical across the Army, Navy, Marines, Air Force, Space Force, and Coast Guard, because the requirements are set by Department of Defense policy and follow CDC recommendations as a baseline, with military-specific additions layered on top. Where branches differ is mainly in logistics and timing. The Marine Corps, for example, vaccinates recruits at the Marine Corps Recruit Depot on arrival, and the compressed 13-week boot camp schedule means there is little flexibility in when each dose is given. The Air Force basic training at Joint Base San Antonio-Lackland has historically done extensive seroprevalence screening, which is where much of the published research on recruit immunity levels comes from.¹

Army recruits at Fort Moore (formerly Fort Benning), Fort Sill, and Fort Jackson go through a similar process, typically during their first week of reception before the more intense phase of training begins. The Navy handles immunization at Recruit Training Command in Great Lakes, Illinois. In all cases, the goal is the same: get recruits fully protected before they are packed into close quarters for weeks of strenuous activity. The vaccine lineup may shift slightly from year to year as new formulations become available or as threat assessments change, but the fundamental approach of front-loading immunization in the first days of service has not changed in generations.