Adenovirus Vaccine Side Effects: What to Expect and When to Call Your Doctor

The Adenovirus Type 4 and Type 7 Vaccine, Live, Oral is a live virus vaccine administered exclusively to military personnel. As with all vaccines, it can cause side effects—most of which are mild and temporary. Understanding what to expect after receiving this vaccine helps recruits distinguish normal post-vaccination reactions from symptoms that warrant medical evaluation.

This guide is based on clinical trial data from a multicenter, double-blind, randomized, placebo-controlled study enrolling 3,031 vaccine recipients and 1,009 placebo recipients who were active duty U.S. Army and Navy military recruits. It also incorporates post-marketing safety data from the Vaccine Adverse Event Reporting System (VAERS).

Common Side Effects (Reported in ≥5% of Vaccine Recipients)

The most frequently reported side effects in the first 7 days after vaccination include:

Nasal congestion — reported in 15.3% of vaccine recipients

Pharyngolaryngeal pain (sore throat/throat pain) — reported in 12.9% of vaccine recipients

Cough — reported in 12.4% of vaccine recipients

Upper respiratory tract infections

Headache

Arthralgia (joint pain)

Nausea

Abdominal pain

Diarrhea

Vomiting

Additionally, pyrexia (fever ≥100.5°F) within the first 7 days was reported in 1.4% of vaccine recipients, compared to 0.5% of placebo recipients. These symptoms typically resolve on their own within a few days and do not require medical treatment beyond rest and standard supportive care (fluids, over-the-counter acetaminophen for fever or pain).

Less Common but Reported Side Effects

A small number of trial participants reported more significant gastrointestinal events that were possibly related to the vaccine, including:

Febrile gastroenteritis (stomach flu with fever)

Gastritis (stomach inflammation)

Hematochezia (blood in stool) — rare; reported in 1 serious adverse event in the vaccine group during the longer follow-up period

Pneumonia — rare; reported in 1 participant at day 23 post-vaccination

Serious Side Effects: What Post-Marketing Data Showed

VAERS surveillance from October 2011 through July 2018 captured 100 adverse event reports following adenovirus vaccination in the U.S. military. Of these:

39 (39%) were classified as serious adverse events

The most frequently reported serious adverse events were Guillain-Barré syndrome (GBS) (n=12) and anaphylaxis (n=8)

One death was reported (causality not established)

Investigators concluded: no unexpected or concerning pattern of adverse events was identified

From post-marketing surveillance, rare adverse events reported in the medical literature (not necessarily causally related) include:

Hypersensitivity reactions including anaphylaxis

Guillain-Barré syndrome (a serious neurological condition)

When Should You Call Your Doctor or Seek Emergency Care?

Contact your military medical provider or seek emergency care immediately if you experience any of the following after receiving the Adenovirus Vaccine:

Signs of anaphylaxis: Hives, swelling of the face or throat, difficulty breathing, rapid heartbeat, dizziness, or severe weakness — call 9-1-1 immediately

Blood in stool or urine: Report to sick call immediately

Signs of Guillain-Barré syndrome: Progressive muscle weakness starting in the legs, numbness or tingling in hands and feet, difficulty walking, facial weakness — seek emergency evaluation

Severe persistent fever (>104°F) or fever lasting more than 3 days

Severe abdominal pain, inability to keep fluids down, or signs of dehydration

Chest pain or severe shortness of breath not associated with known causes

What's Normal vs. What's Not

Normal and expected: Mild nasal congestion, mild sore throat, mild cough, mild headache, and mild GI symptoms (nausea, loose stools) in the first 7–10 days after vaccination. Low-grade fever (under 101°F) for 1–2 days. These do not require sick call unless they persist or worsen.

Report to sick call: Symptoms that worsen beyond day 3–5, fever above 102°F, inability to eat or drink, visible blood in stool or urine, or any neurological symptoms.

For information about medications and interactions that can affect how this vaccine works, see: Adenovirus Vaccine Drug Interactions: What to Avoid and What to Tell Your Doctor.

For background on what this vaccine is and why it's only available to military personnel, see: Why Is the Adenovirus Vaccine So Hard to Find?