Vaccines · The Medical Record
What These Diseases Do
Anti-vaccine promoters call them mild childhood illnesses. Here is what congenital rubella, hepatitis B, measles, chickenpox, meningitis, RSV and rotavirus actually do to children, how often, and where to read more.
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| Disease | Main complications | How often, how serious |
|---|---|---|
| Congenital rubella | Deafness (the most common defect); cataracts, glaucoma, retinal damage; heart defects (patent ductus arteriosus, pulmonary artery stenosis); microcephaly, developmental delay, meningoencephalitis; in newborns, purpura, enlarged liver and spleen, jaundice, bone lesions | 90% of infants are affected if the mother is infected in the first 11 weeks; about 20% in the first 20 weeks. After 20 weeks the only defect may be deafness. The 1962–65 US epidemic left 20,000 babies with the syndrome and caused 11,250 fetal deaths. |
| Hepatitis B acquired at birth | Usually no illness at birth; the baby becomes a lifelong carrier. Decades later: cirrhosis, liver failure, liver cancer. The carrier can also pass the virus on. | About 90% of infants infected at birth become chronic carriers, against 1–5% of adults. Over decades, 20–25% of carriers develop cirrhosis and about 5–6% liver cancer. |
| Measles acquired in the womb | Miscarriage, stillbirth, low birth weight; congenital measles (a newborn ill within 10 days of birth), most dangerous in preterm babies; serious illness and death in the mother. Measles has not been shown to cause a pattern of birth defects. | In one outbreak study (Namibia), miscarriage was about 6 times as common and fetal death 9 times as common as in pregnancies without measles. 9% of the infected mothers died, though HIV was a factor in some deaths. |
| Measles at any age | Ear infection, pneumonia (the usual cause of measles deaths), diarrhea, encephalitis; “immune amnesia,” which erases existing immunity to other infections; SSPE, a fatal brain disease 7–10 years later | About 1 in 1,000 develop encephalitis and about 1 in 3,000 die. SSPE strikes 1 in 1,367 children infected under age 5, and 1 in 609 infected as infants. Immune amnesia wipes out 11–73% of a child’s antibodies. |
| Chickenpox | Bacterial skin and soft-tissue infection, including necrotizing fasciitis; pneumonia; bone and joint infection; encephalitis, cerebellar ataxia, stroke; shingles later in life. In pregnancy: congenital varicella syndrome. Around birth: severe neonatal chickenpox. | Raises a healthy child’s risk of severe invasive Group A strep infection 40–60 times. Before the vaccine, Canada had about 350,000 cases, 1,550 hospitalizations and roughly 5–6 deaths a year. Infection at 13–19 weeks of pregnancy carries a 2% risk of congenital varicella syndrome (limb, eye and brain damage; nearly a third of affected babies die). A mother’s rash from 5 days before to 2 days after delivery causes severe newborn chickenpox in 17–30% of babies. |
| Meningitis | Hib: deafness, brain damage, seizures, death. Pneumococcal: the highest death rate of the common bacterial types; hearing loss and brain damage in survivors. Meningococcal: can kill within hours; survivors may lose limbs, skin or hearing. Group B strep (newborns): seizures, developmental delay, death. Viral (enterovirus, mumps): usually a full recovery; mumps can cause permanent deafness. | Hib: about 5% die; 15–20% of survivors are left deaf and 10–15% with severe neurological damage. Meningococcal: 10–15% die, and 10–20% of survivors have lasting damage such as amputation, hearing loss or brain injury. |
| RSV | Bronchiolitis and pneumonia; apnea (pauses in breathing) in very young and premature babies; respiratory failure needing ICU care and a ventilator; later recurrent wheezing (an association, not a proven cause) | Nearly every child catches RSV by age two, and it is a leading cause of infant hospitalization. The highest risk is under six months and in premature babies or those with heart or lung disease. Ontario’s antibody program prevented 97% of ICU admissions in its first season. |
| Rotavirus in early childhood | Severe vomiting and diarrhea leading to dehydration; salt and acid imbalance; seizures; shock; death | Before the vaccine it was the leading cause of gastroenteritis admissions in young Canadian children. Ontario’s program cut rotavirus hospitalizations by 71%, and by 79% in babies under one. Deaths are rare in Canada but common worldwide where IV fluids are hard to reach. |
Tap a disease name for its sources and further reading. Two cautions: the measles-in-pregnancy figures come from a single outbreak study in Namibia, where HIV contributed to some mothers’ deaths; and pneumococcal and Group B strep meningitis are described in words only, because we have not yet verified specific Canadian figures.
Congenital rubella
What it doesDeafness (the most common defect); cataracts, glaucoma, retinal damage; heart defects (patent ductus arteriosus, pulmonary artery stenosis); microcephaly, developmental delay, meningoencephalitis; in newborns, purpura, enlarged liver and spleen, jaundice, bone lesions
How often, how serious90% of infants are affected if the mother is infected in the first 11 weeks; about 20% in the first 20 weeks. After 20 weeks the only defect may be deafness. The 1962–65 US epidemic left 20,000 babies with the syndrome and caused 11,250 fetal deaths.
Source: CDC, Congenital rubella syndrome, surveillance manual; CDC MMWR 54(11), 2005
Read more
- QuackeryWatch: Before the Vaccines, rubella
- CDC surveillance manual: Congenital rubella syndrome
- CDC surveillance manual: Rubella
- In their own words: rubella’s children, now in their sixties
- “Gregg’s congenital rubella patients 60 years later” (MJA, 2002)
- Helen Keller National Center: congenital rubella syndrome
Hepatitis B acquired at birth
What it doesUsually no illness at birth; the baby becomes a lifelong carrier. Decades later: cirrhosis, liver failure, liver cancer. The carrier can also pass the virus on.
How often, how seriousAbout 90% of infants infected at birth become chronic carriers, against 1–5% of adults. Over decades, 20–25% of carriers develop cirrhosis and about 5–6% liver cancer.
Source: Public Health Agency of Canada, Hepatitis B infection in Canada
Measles acquired in the womb
What it doesMiscarriage, stillbirth, low birth weight; congenital measles (a newborn ill within 10 days of birth), most dangerous in preterm babies; serious illness and death in the mother. Measles has not been shown to cause a pattern of birth defects.
How often, how seriousIn one outbreak study (Namibia), miscarriage was about 6 times as common and fetal death 9 times as common as in pregnancies without measles. 9% of the infected mothers died, though HIV was a factor in some deaths.
Closer to home: In June 2025, Ontario’s Chief Medical Officer of Health reported that six babies had been born with congenital measles since the fall of 2024, all to unvaccinated mothers. A premature baby infected in the womb died in southwestern Ontario; the province noted the infant also had other serious medical problems.
Source: Ogbuanu et al., measles in pregnancy, Namibia (2014)
Measles at any age
What it doesEar infection, pneumonia (the usual cause of measles deaths), diarrhea, encephalitis; “immune amnesia,” which erases existing immunity to other infections; SSPE, a fatal brain disease 7–10 years later
How often, how seriousAbout 1 in 1,000 develop encephalitis and about 1 in 3,000 die. SSPE strikes 1 in 1,367 children infected under age 5, and 1 in 609 infected as infants. Immune amnesia wipes out 11–73% of a child’s antibodies.
Source: HealthLink BC, Measles; Wendorf KA et al., Clin Infect Dis 2017;65(2):226–232; Mina MJ et al., Science 2019
Chickenpox
What it doesBacterial skin and soft-tissue infection, including necrotizing fasciitis; pneumonia; bone and joint infection; encephalitis, cerebellar ataxia, stroke; shingles later in life. In pregnancy: congenital varicella syndrome. Around birth: severe neonatal chickenpox.
How often, how seriousRaises a healthy child’s risk of severe invasive Group A strep infection 40–60 times. Before the vaccine, Canada had about 350,000 cases, 1,550 hospitalizations and roughly 5–6 deaths a year. Infection at 13–19 weeks of pregnancy carries a 2% risk of congenital varicella syndrome (limb, eye and brain damage; nearly a third of affected babies die). A mother’s rash from 5 days before to 2 days after delivery causes severe newborn chickenpox in 17–30% of babies.
Source: Public Health Agency of Canada, Varicella (chickenpox)
Meningitis
What it doesHib: deafness, brain damage, seizures, death. Pneumococcal: the highest death rate of the common bacterial types; hearing loss and brain damage in survivors. Meningococcal: can kill within hours; survivors may lose limbs, skin or hearing. Group B strep (newborns): seizures, developmental delay, death. Viral (enterovirus, mumps): usually a full recovery; mumps can cause permanent deafness.
How often, how seriousHib: about 5% die; 15–20% of survivors are left deaf and 10–15% with severe neurological damage. Meningococcal: 10–15% die, and 10–20% of survivors have lasting damage such as amputation, hearing loss or brain injury.
Source: Public Health Agency of Canada, Haemophilus influenzae disease: for health professionals; CDC, meningococcal disease
Read more
- QuackeryWatch: Before the Vaccines, meningitis
- QuackeryWatch: The boy on the float plane (pneumococcal meningitis, 1974)
- CDC surveillance manual: Haemophilus influenzae (Hib)
- CDC surveillance manual: Meningococcal disease
- CDC surveillance manual: Pneumococcal disease
- CDC surveillance manual: Mumps (mumps meningitis)
- In their own words: parents’ stories, collected
RSV
What it doesBronchiolitis and pneumonia; apnea (pauses in breathing) in very young and premature babies; respiratory failure needing ICU care and a ventilator; later recurrent wheezing (an association, not a proven cause)
How often, how seriousNearly every child catches RSV by age two, and it is a leading cause of infant hospitalization. The highest risk is under six months and in premature babies or those with heart or lung disease. Ontario’s antibody program prevented 97% of ICU admissions in its first season.
Source: SPRINT-KIDS, JAMA Network Open 2026 (via University of Calgary, 14 Sept 2026)
Rotavirus in early childhood
What it doesSevere vomiting and diarrhea leading to dehydration; salt and acid imbalance; seizures; shock; death
How often, how seriousBefore the vaccine it was the leading cause of gastroenteritis admissions in young Canadian children. Ontario’s program cut rotavirus hospitalizations by 71%, and by 79% in babies under one. Deaths are rare in Canada but common worldwide where IV fluids are hard to reach.
Source: Public Health Ontario, rotavirus hospitalizations (May 2016)
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