vial of Johnson & Johnson's COVID-19 vaccine

Experts suggest that booster shots may help extend the effects of the COVID-19 vaccine, and those who received the Janssen/Johnson & Johnson vaccine at least 2 months ago are now eligible for the booster shot (via PBS News Hour). For those opting to get their booster shots, you may be wondering what the potential side effects are. While Johnson & Johnson’s booster clinical trial suggests side effects were less frequently reported than during the initial shot, the CDC reports that side effects for the booster are similar to the initial vaccine and typically happen within a day or two after being administered. It may help to know that the FDA concluded that while side effects can be unpleasant, the shot is generally well-tolerated and the potential benefits outweigh the unlikely serious risks (via AARP). Note that there are three approved vaccine boosters currently available on the market today, including Pfizer-BioNTech, Moderna and Janssen/Johnson & Johnson. The FDA has approved the safety and efficacy of receiving a booster shot that is a different brand than the initial vaccination brand.

Injection site pain

woman holding her arm in pain

With 40% of the population reporting injection site pain, this is the most common side effect amongst the vaccinated. Note that regardless of which vaccine or booster you get, the vaccine is injected into the deltoid muscle of our arm, the area of the arm largely responsible for range of motion. Subsequent pain, swelling, and redness at the booster shot injection site can happen for various reasons. One reason may be due to an immune response initiated by the vaccine. In a nutshell, the science behind the vaccine is to make our bodies think we’ve been infected by the virus, via Verywell Health. In trying to defend our bodies, our immune system sends white blood cells to fight the invader. This can cause inflammation and pain as a result. Secondly, because the shot is administered in a part of the arm we move frequently, simple movements throughout the day may signal pain. Arm pain is generally harmless but an annoyance. However, it typically resolves within a few days. In order to minimize the pain, it’s recommended to apply a cold compress and use/exercise the arm frequently, via CDC.

Fatigue and headache

woman in bed holding her head in pain

Fatigue and headache are categorized as mild effects of the booster shot and occur in roughly 29% of the population, making these two ailments the second most common side effects, via AARP. As such, many are turning to over-the-counter medications such as ibuprofen, acetaminophen, and aspirin to help alleviate the pain. However, it’s suggested that these medications be used only after receiving the booster shot and on an as-needed basis rather than before the shot as a preventative measure, via the CDC. Additionally, anyone considering over-the-counter medications should consult their physician first. Some individuals may have medical conditions that make such medications unsafe to take. Interestingly, when it came to individuals with post-vaccine fatigue, researchers suggested the placebo effect may have been to blame. One study showed that 23% of participants complained of fatigue after receiving a placebo dose of the COVID-19 vaccine, via National Geographic. The same may hold true for the booster shot.

Body aches and nausea

woman holding a cold compress to her stomach

Body aches were reported in 26% of the vaccinated population. This may manifest as a dull ache and pain that radiates throughout the body. If you’ve ever experienced body aches while fighting the flu, the effect is similar after the booster shot. Similar to headache, it’s recommended that those experiencing body aches consider using over-the-counter pain relief to manage the discomfort, via the CDC. Other simple ways to alleviate body pain can include a cool bath or soaking in Epsom salts, via Yale Health. In addition to body aches, 12% of the population reported nausea as another uncomfortable side effect of the vaccine and booster shot. While nausea and body aches may impede one’s ability to perform daily tasks to the best of their ability, these side effects typically resolve in 1-2 days and are generally not considered dangerous or life-threatening. Simple ways to minimize nausea include drinking ginger tea and drinking plenty of fluids that replenish electrolytes. While nausea can be a symptom of the booster, it’s also a common symptom of general dehydration. If we’re not feeling well to begin with, we may be drinking fewer fluids than normal.

Other side effects

woman with fear of needles turning her head during vaccination

Fainting has been reported as a possible, yet uncommon, side effect post-vaccine. Health experts suggest this has less to do with the vaccine itself and more to do with the anxiety surrounding any shot or vaccination. Related symptoms that generally accompany fainting post-shot administration are rapid breathing, a drop in blood pressure, and tingling sensations throughout the body. According to the Vaccine Adverse Event Reporting System (VAERS), 653 cases of fainting occurred out of 8 million Johnson & Johnson vaccine administrations, via CDC. Such incidences occurred during the 15-minute monitoring session post-vaccination.

Additionally, allergic reactions may occur as a result of the booster shot. One such reaction is anaphylaxis, a life-threatening allergic reaction. Compared to the Moderna and Pfizer vaccine, there are fewer reported cases of allergic reactions in the Johnson & Johnson vaccinated population, via CNBC. It’s recommended that if you had an allergic reaction to an initial dose of the vaccine, do not get another dose of the same brand.

Adverse effects and when to seek medical attention

team of doctors standing in front of hospital

Interestingly, research suggests women may have higher risks for common side effects as well as adverse effects than men. Several theories abound including differences in hormones, the fact that women typically have stronger immune responses, and women tend to report symptoms and seek medical attention more frequently than men, via National Geographic. While common side effects may affect daily living, they shouldn’t last more than a few days. Adverse effects, on the other hand, can pose a dangerous health risk. One such risk associated with Janssen/Johnson & Johnson COVID-19 vaccine included the risk of thrombocytopenia syndrome (TTS). TSS is a serious type of blood clot that presents in tandem with low blood platelets. People developed TSS after receiving the vaccine and developed symptoms 1-2 weeks later. This condition has been most highly reported by women between the ages of 18-49, via the FDA. Another serious side effect called Guillain-Barré syndrome, a severe neurological disorder, was reported within 42 days of receiving the Janssen/Johnson & Johnson COVID-19 vaccine. Other serious side effects that require emergency care include: shortness of breath, stomach pain that won’t go away, severe headaches and blurred vision, pain in the chest, and swelling of the legs, via Mayo Clinic.