What was meant to protect her, only led to more danger: How did this woman contract the "world's deadliest" virus?
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In rare cases, even routine medical visits can take unexpected turns.
One such incident involving a medical misstep has prompted renewed conversations around healthcare protocols and patient safety.
While such errors are uncommon, it’s a reminder of the importance of awareness and clear communication in medical settings.
Vaccines continue to be one of the greatest achievements in public health, helping prevent countless illnesses and save millions of lives each year.
But a recent case reported in the American Journal of Case Reports serves as a powerful reminder that how a vaccine is administered matters just as much as what vaccine is given.
In this extremely rare instance, a woman developed a serious infection—not because of the vaccine’s contents, but because it was administered the wrong way.
A healthy 30-year-old woman in Ireland had gone in for a routine measles, mumps, and rubella (MMR) vaccine.
However, due to a critical mix-up by the medical provider, she was accidentally given the BCG vaccine, which protects against tuberculosis (TB)—the world’s deadliest bacterial infection.
Tuberculosis kills an estimated 1.2 million people globally each year, though it's rare in countries like the United States thanks to modern medicine and widespread vaccination where necessary.
The BCG vaccine, which contains a weakened form of Mycobacterium bovis, is widely used and safe when administered correctly, typically in early childhood in areas where TB is still common.
The error in this case wasn’t just about the wrong vaccine being given—it was also about how it was given.
The BCG vaccine is meant to be injected just under the skin (intradermally), not into the muscle. This distinction is important: vaccines like MMR, which use weakened viruses, are designed to be injected into the muscle, where the body processes them effectively.
But bacterial vaccines like BCG behave differently, and injecting them into the muscle can allow bacteria to multiply in ways that the immune system struggles to control.
This unfortunate combination—receiving the wrong vaccine and receiving it through the wrong route—led to the woman developing a severe local TB infection in her upper arm.
It wasn’t until they tested the fluid from the abscess that they found TB-causing bacteria, possibly from the cattle-associated strain used in the BCG vaccine. This finding explained her symptoms.
The bacteria had spread through her deltoid muscle, where the immune system couldn’t mount the usual localized defense. That allowed the infection to develop more aggressively than it would have if the vaccine had been injected correctly under the skin.
According to the doctors who documented the case, “Administration of the BCG vaccine intramuscularly is commonly the result of an error and can lead to rare and preventable complications, even in immunocompetent patients.”
They note that such complications are almost always preventable and stem from the route of administration, not from the vaccine itself.
Also read: What happened at CVS? Company responds to customer concern following major misstep
Doctors began treating her with a combination of anti-tuberculosis medications, and she responded well. After three months, the abscess had shrunk considerably. After six months, she had made a full recovery, with no lingering symptoms reported.
You might be interested: Are you at risk? Shocking details on the outbreak threatening Kansas with 67 cases reported!
MMR vaccines are injected into the muscle, and it’s likely the healthcare provider administered the BCG the same way, unaware that BCG should never be injected intramuscularly.
This isn’t the first time such a mix-up has occurred. The National Institutes of Health (NIH) has previously documented a similar case involving an eight-month-old infant who was accidentally given the BCG vaccine into the thigh muscle at birth.
That child also developed a swelling at the injection site that grew over time and later tested positive for Mycobacterium bovis. Thankfully, that child also recovered after treatment.
Doctors stress that localized TB infections caused by BCG vaccine errors are not typically fatal—especially when diagnosed and treated properly.
However, if left untreated, these infections can potentially spread throughout the body, where they become much more dangerous and, in rare cases, life-threatening.
Also read: Discovery in US bogs could revolutionize tuberculosis treatment!
Vaccination remains one of the most reliable ways to stay healthy, particularly for seniors who are more vulnerable to complications from diseases like flu, COVID-19, pneumonia, and shingles.
This case should not undermine that trust—it should serve as a reminder of the importance of clear protocols and proper training in clinical settings.
In the end, the woman made a full recovery thanks to swift diagnosis and modern treatment.
Her case may be rare, but it highlights the value of vigilance—not fear—when it comes to protecting our health.
Read next: Shocking health alert: Tuberculosis now the deadliest disease – Are you at risk?
Have you or someone you know ever experienced a vaccine administration error? What steps did you take to address the situation? Share your stories and insights in the comments below!
One such incident involving a medical misstep has prompted renewed conversations around healthcare protocols and patient safety.
While such errors are uncommon, it’s a reminder of the importance of awareness and clear communication in medical settings.
Vaccines continue to be one of the greatest achievements in public health, helping prevent countless illnesses and save millions of lives each year.
But a recent case reported in the American Journal of Case Reports serves as a powerful reminder that how a vaccine is administered matters just as much as what vaccine is given.
In this extremely rare instance, a woman developed a serious infection—not because of the vaccine’s contents, but because it was administered the wrong way.
A healthy 30-year-old woman in Ireland had gone in for a routine measles, mumps, and rubella (MMR) vaccine.
However, due to a critical mix-up by the medical provider, she was accidentally given the BCG vaccine, which protects against tuberculosis (TB)—the world’s deadliest bacterial infection.
A healthy woman in Ireland mistakenly received a TB vaccine instead of the MMR shot and developed a severe TB infection as a result. Image source: National Cancer Institute / Unsplash.
Tuberculosis kills an estimated 1.2 million people globally each year, though it's rare in countries like the United States thanks to modern medicine and widespread vaccination where necessary.
The BCG vaccine, which contains a weakened form of Mycobacterium bovis, is widely used and safe when administered correctly, typically in early childhood in areas where TB is still common.
The error in this case wasn’t just about the wrong vaccine being given—it was also about how it was given.
The BCG vaccine is meant to be injected just under the skin (intradermally), not into the muscle. This distinction is important: vaccines like MMR, which use weakened viruses, are designed to be injected into the muscle, where the body processes them effectively.
But bacterial vaccines like BCG behave differently, and injecting them into the muscle can allow bacteria to multiply in ways that the immune system struggles to control.
This unfortunate combination—receiving the wrong vaccine and receiving it through the wrong route—led to the woman developing a severe local TB infection in her upper arm.
What Happened Next
Shortly after the injection, the woman developed an abscess on her upper arm, which began oozing pus. Her doctors initially suspected a skin or tissue inflammation.It wasn’t until they tested the fluid from the abscess that they found TB-causing bacteria, possibly from the cattle-associated strain used in the BCG vaccine. This finding explained her symptoms.
The incorrect administration of the BCG vaccine intramuscularly led to the development of an abscess and a whole-body infection. Image source: CDC / Unsplash.
The bacteria had spread through her deltoid muscle, where the immune system couldn’t mount the usual localized defense. That allowed the infection to develop more aggressively than it would have if the vaccine had been injected correctly under the skin.
According to the doctors who documented the case, “Administration of the BCG vaccine intramuscularly is commonly the result of an error and can lead to rare and preventable complications, even in immunocompetent patients.”
They note that such complications are almost always preventable and stem from the route of administration, not from the vaccine itself.
Also read: What happened at CVS? Company responds to customer concern following major misstep
How Serious Was It?
While most side effects from the BCG vaccine are mild and limited to slight swelling or blistering at the injection site, about 1 to 10 percent of recipients in medical literature have experienced more severe complications—especially when the vaccine is given improperly. These can include:- Abscesses and pus-filled lesions
- Inflamed bones (osteitis)
- Enlarged lymph nodes
- Widespread bacterial infection in very rare cases
- Liver or spleen inflammation
- Systemic infection in immunocompromised individuals
The misadministration is a rare but preventable error, commonly due to injection technique confusion by healthcare professionals. Image source: Ed Us / Unsplash.
Doctors began treating her with a combination of anti-tuberculosis medications, and she responded well. After three months, the abscess had shrunk considerably. After six months, she had made a full recovery, with no lingering symptoms reported.
You might be interested: Are you at risk? Shocking details on the outbreak threatening Kansas with 67 cases reported!
Why Did This Happen?
The doctors involved believe the mistake stemmed from a confusion between the MMR and BCG vaccines, and from using the wrong technique based on that assumption.MMR vaccines are injected into the muscle, and it’s likely the healthcare provider administered the BCG the same way, unaware that BCG should never be injected intramuscularly.
This isn’t the first time such a mix-up has occurred. The National Institutes of Health (NIH) has previously documented a similar case involving an eight-month-old infant who was accidentally given the BCG vaccine into the thigh muscle at birth.
That child also developed a swelling at the injection site that grew over time and later tested positive for Mycobacterium bovis. Thankfully, that child also recovered after treatment.
Doctors stress that localized TB infections caused by BCG vaccine errors are not typically fatal—especially when diagnosed and treated properly.
However, if left untreated, these infections can potentially spread throughout the body, where they become much more dangerous and, in rare cases, life-threatening.
Also read: Discovery in US bogs could revolutionize tuberculosis treatment!
What Seniors Should Know
This case, while extremely rare and specific, offers a teachable moment, especially for older adults who may regularly receive vaccinations. Here’s what’s important to take away:- Vaccines are safe and effective when administered correctly.
- This case involved a clear human error, not a failure of vaccine safety.
- It’s okay—and encouraged—to ask your provider questions before receiving a shot, such as:
- What vaccine is being administered?
- Is this the right method of administration?
- Healthcare providers are trained to follow these protocols, but rare errors can still happen.
- If something doesn’t feel right, speak up. Patient advocacy is important, and you have a right to know what’s being administered.
After an intensive treatment regimen, the woman fully recovered six months after the initiation of anti-tuberculosis treatment. Image source: Mufid Majnun / Unsplash.
Vaccination remains one of the most reliable ways to stay healthy, particularly for seniors who are more vulnerable to complications from diseases like flu, COVID-19, pneumonia, and shingles.
This case should not undermine that trust—it should serve as a reminder of the importance of clear protocols and proper training in clinical settings.
In the end, the woman made a full recovery thanks to swift diagnosis and modern treatment.
Her case may be rare, but it highlights the value of vigilance—not fear—when it comes to protecting our health.
Read next: Shocking health alert: Tuberculosis now the deadliest disease – Are you at risk?
Have you or someone you know ever experienced a vaccine administration error? What steps did you take to address the situation? Share your stories and insights in the comments below!
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