Diseases

Measles

A very contagious virus causing fever and rash; can cause pneumonia and brain swelling.

Share-of-cases figures do not on their own give the risk for a vaccinated vs unvaccinated person (that needs the size of each group).

Mumps

A virus that swells the salivary glands; can cause deafness, meningitis, swollen testicles.

Rubella (German measles)

Usually mild in children, but infection in early pregnancy can cause miscarriage or serious birth defects (congenital rubella syndrome).

Chickenpox (varicella)

Itchy blister rash, usually mild in children; can cause skin infections, pneumonia, brain swelling. Now routine in UK (MMRV from Jan 2026) and US.

Whooping cough (pertussis)

Bacterial infection with long coughing fits; most dangerous for babies under 6 months.

Diphtheria

Bacterial throat infection whose toxin can block airways and damage heart and nerves.

Tetanus (lockjaw)

Not caught from people - bacteria in soil enter wounds; toxin causes painful muscle spasms.

Polio

Virus spread through faeces; most infections are mild but some cause permanent paralysis.

Hib (Haemophilus influenzae type b)

Bacteria causing meningitis, blood infection and throat swelling, mainly in under-5s.

Hepatitis B

Blood-borne liver virus; babies infected at birth usually become lifelong carriers, risking cirrhosis and liver cancer.

UK gives the birth dose only to babies of mothers with hep B; US birth-dose policy was changed in Dec 2025 then restored by court order in March 2026.

Hepatitis A

Liver virus spread through contaminated food/water or close contact; usually mild in young children. Routine in US only.

Meningococcal group B (MenB)

Bacteria causing meningitis and blood poisoning (sepsis); can kill within hours.

Meningococcal groups A, C, W, Y

Same illness as above, other strains; teenage MenACWY dose in both countries.

Pneumococcal disease

Bacteria causing pneumonia, ear infections, blood infection and meningitis.

Rotavirus

Stomach bug causing severe diarrhoea and vomiting in babies; dehydration is the danger.

HPV (human papillomavirus)

Very common sexually transmitted virus; some types cause cervical and other cancers and genital warts.

Flu (influenza)

Seasonal respiratory virus; most serious in the very old, very young and people with health conditions.

COVID-19

Respiratory virus. UK offers the vaccine only to at-risk groups; US lists it as 'shared clinical decision-making' for children.

RSV (respiratory syncytial virus)

Common winter virus; can cause bronchiolitis and breathing trouble in babies. Protected by a vaccine in pregnancy (UK and US) or an antibody shot for babies (US).

Vitamin K deficiency bleeding (not a vaccine)

Babies are born low in vitamin K; rarely this causes bleeding, sometimes in the brain. The birth injection is vitamin K, not a vaccine.

Newborn vitamin D (a supplement, not a vaccine)

Vitamin D drops (usually cholecalciferol, vitamin D3) are advised for breastfed babies from birth, to prevent rickets. Shown here next to vitamin K, the other newborn supplement in this guide.

What is given, and how

• NHS advises that breastfed babies "should be given a daily vitamin D supplement from birth, whether or not you're taking a supplement containing vitamin D yourself". NHS says the drops can be bought "at pharmacies and supermarkets". source source 2
• The UK Healthy Start leaflet says its drops "should be given by mouth (orally)", 5 drops once daily. source
• NIH ODS reports that supplements contain vitamin D2 (ergocalciferol) or D3 (cholecalciferol); D3 "is typically produced with irradiation of 7-dehydrocholesterol from lanolin obtained from the wool of sheep", and a lichen-sourced D3 also exists. source
• The Australasian Neonatal Medicines Formulary lists two routes for newborn colecalciferol, oral and intramuscular. Its prevention dose is 400 units a day by mouth. Intramuscular use is listed for treating rickets: "If oral administration is difficult, consider intramuscular vitamin D3 100,000 units (colecalciferol 2.5 mg) every 3 months (3 doses)." The injectable product it names holds 600,000 units per mL. source
• The 2016 global consensus on rickets describes "stoss therapy" as "the administration of a large dose given as a single dose or in divided doses over several days". It recommends daily treatment first but says "in some situations, stoss therapy may be more practical". On route, it says: "We recommend oral treatment, which more rapidly restores 25OHD levels than IM treatment." These are treatment doses for rickets, not routine newborn doses. source
• Thailand: a 2021 Thai trial reports that "routine vitamin D supplementation for exclusively breastfed infants has not been widely practiced" in Thailand and that "the local healthcare authorities have not established a national consensus". It also says no infant vitamin D-only product was on sale in Thailand when the study was done, so it used a multivitamin drop. source
• A 2024 Bangkok study states: "in Thailand, no advice for routine vitamin D supplementation is available." source
• GAP: this guide found no published source saying that Thai hospitals routinely give vitamin D as an injection on the day of birth, and no national Thai policy saying so. Practice may vary by hospital. The product name and dose on a baby's hospital discharge record would show what was given.

Recommended dose and why (UK and US)

• UK (NHS / Department of Health and Social Care): babies from birth to 1 year who are breastfed "should be given a daily supplement containing 8.5 to 10 micrograms of vitamin D". Babies having more than 500ml of infant formula a day should not be given one, because formula is already fortified. source
• NICE CKS gives the same UK dose in units: 8.5-10 micrograms is 340-400 international units (IU) a day. (1 microgram = 40 IU.) source source 2
• US (AAP): "Vitamin D supplements of 400 IU (10 mcg) per day are recommended for babies up until age one year." source
• CDC: the AAP and the Dietary Guidelines for Americans "recommend that breastfed and partially breastfed infants receive 400 International Units (IU) of vitamin D daily beginning in the first few days of life." source
• Why: the AAP's clinical report is titled "Prevention of Rickets and Vitamin D Deficiency in Infants, Children, and Adolescents". CDC states that vitamin D "helps prevent rickets, a condition that causes weak or deformed bones." source source 2
• NHS describes rickets as a condition caused by a lack of vitamin D or calcium; it says the main symptom is bowed legs. source
• The 2016 global consensus states: "400 IU/d (10 μg) is adequate to prevent rickets and is recommended for all infants from birth to 12 months of age, independent of their mode of feeding." source
• How common rickets is: NIH ODS reports 24.1 cases per 100,000 children under 3 in one Minnesota county (2000s), mainly in breastfed Black children, and 2.9 per 100,000 children under 7 in Canada (2002-2004), where "almost all patients with rickets had been breastfed". source

Ingredients in the drops (from manufacturers' leaflets and labels)

• Enfamil D-Vi-Sol (US): 10 mcg (400 IU) vitamin D per 1 mL. Other ingredients: "Glycerin, water, polysorbate 80 (emulsifier), citric acid (antioxidant for vitamin D), natural flavor, sodium citrate." source
• Baby Ddrops: 400 IU per drop, "made with only two naturally sourced ingredients, pure vitamin D3 and organic fractionated coconut oil". The maker states it is free from preservatives. source
• Healthy Start children's vitamin drops (UK government scheme): 5 drops contain vitamin D 7.5 micrograms (300 IU), vitamin A 233 micrograms and vitamin C 20 mg. Other ingredients: "water, glycerol, polysorbate 80, banana flavour, alpha-tocopherol, Medium Chain Triglycerides." (This leaflet was last approved in 05/2018.) source
• The ANMF notes that some vitamin D preparations contain sodium benzoate, and advises: "Avoid exposure to sodium benzoate of >99 mg/kg/day in neonates." source
• The Thai trial used Munti-Vim multivitamin drops (B.L. Hua, Bangkok), with 400 IU vitamin D3 per mL plus vitamins A, B1, B2, B6, B12, C, nicotinamide and dexpanthenol. source

Cholecalciferol as a rat poison (EPA)

• US EPA: "Cholecalciferol is vitamin D3, which in small dosages is needed for good health in most mammals, but in massive doses is toxic, especially to rodents." source
• EPA's label database lists Cholecalciferol Blox (EPA Reg. No. 12455-162), a registered rat and mouse bait, with cholecalciferol at 0.075% as the active ingredient. source
• An EPA risk assessment memo states that cholecalciferol works as a rodenticide by mobilising "calcium from bones into the blood plasma causing hypercalcemia". The same memo notes that it is a nutrient permitted as a food additive and is generally recognised as safe as a dietary supplement "within specific limitations". source
• NPIC reports that cholecalciferol was first registered as a rodenticide in the US in 1984. "The body's ability to maintain proper calcium levels must be overwhelmed before cholecalciferol becomes toxic. Rodents must eat several doses." It adds that "poisonings of people are very rare." source
• This guide's own arithmetic 0.075% means 0.75 mg of cholecalciferol per gram of bait, which is 750 micrograms, or 30,000 IU. One infant daily dose is 10 micrograms (400 IU). So 1 gram of bait holds about 75 infant daily doses, and one infant daily dose equals the vitamin D in about 13 mg of bait. source source 2
• This guide's own arithmetic Concentration compared: D-Vi-Sol has 10 micrograms per mL. The bait (750 micrograms per gram) is about 75 times as concentrated, taking 1 mL as about 1 gram. The newborn injection product named by the ANMF (600,000 units/mL = 15 mg/mL) is about 20 times as concentrated as the bait. The effect depends on the total amount swallowed or injected, not on concentration alone. source source 2

Too much vitamin D in infants: evidence, warnings and recalls

• Upper limits: NIH ODS gives the US upper intake level as 1,000 IU (25 mcg) a day for 0-6 months and 1,500 IU (38 mcg) for 7-12 months. NHS says infants under 12 months "should not have more than 25 micrograms (1,000 IU) a day". source source 2
• NIH ODS: too much vitamin D causes high blood calcium, which can lead to nausea, vomiting, muscle weakness, dehydration and kidney stones, and in extreme cases kidney failure, heart rhythm problems and death. It says toxicity has been caused by supplements with excess vitamin D "because of manufacturing errors", supplements taken in excessive amounts, and wrong prescriptions. It also says too much sun does not cause vitamin D toxicity. source
• The ANMF reports that 1,600 units/day of vitamin D3 "produced vitamin D toxicity (hypercalcaemia and 25OH vitamin D >250 nmol/L) in 94% of healthy, term, breastfed infants" in the study it cites, and that a single 600,000-unit dose in infants "produced prolonged vitamin D excess and transient hypercalcaemia, whereas doses of 100,000 to 200,000 units every 3 months did not." source
• In a stoss-therapy study cited by the 2016 consensus, 56 Turkish children aged 3-36 months were given single oral doses of 150,000, 300,000 or 600,000 IU, and eight developed high blood calcium (two in the 300,000 group, six in the 600,000 group). source
• 2010 FDA, June 2010: FDA had seen "an increase in the number of liquid vitamin D dietary supplements being marketed that could lead to infants receiving an unsafe amount of vitamin D", because droppers could hold more than an infant should get. It recommended that droppers for infant products "hold no more than 400 units". source
• 2024 Recall, February 2024 (FDA notice): Nordic Naturals recalled one lot (234909) of Baby's Vitamin D3 Liquid, about 3,800 units, after "a manufacturing error that resulted in an elevated level of Vitamin D3 dosage". The company reported no adverse events at that time. source
• Case report (US): a 3-month-old was given 1 mL a day of a new product that held 400 IU per drop rather than per mL. That came to 12,000 IU a day, a 30-fold overdose, for 20 days. The authors say the infant was "clinically stable with no symptoms" when the error was found. source
• 2023 France (ANSES, 2023): ANSES received three reports in 2022 of severe high blood calcium in infants who were given internet-bought food supplements containing 5,000-10,000 IU per drop, in one case 40,000 IU a day. The reports included kidney calcium deposits (nephrocalcinosis) and, in one infant, an ECG abnormality. ANSES advises against replacing medicinal vitamin D with a food supplement. source
• 2022 Case report (France, 2022): a 3-month-old developed severe high blood calcium after the parents, on a midwife's advice, swapped the prescribed medicinal vitamin D for a "natural" dietary supplement of a different concentration. source

Natural sources, D2 versus D3, and breast milk

• Sunlight: NIH ODS explains that UVB light (about 290-320 nm) on bare skin turns 7-dehydrocholesterol into previtamin D3, which becomes vitamin D3. UVB does not pass through glass. source
• NIH ODS reports that the AAP advises keeping infants under 6 months out of direct sunlight. NHS says: "Young children should still have vitamin drops, even if they get out in the sun." source source 2
• A Bangkok study of 109 exclusively breastfed 4-month-olds found 35.78% vitamin D deficient and 33.03% insufficient. Their "sun index showed no correlation with the 25-OH vitamin D level". source
• Foods (NIH ODS table, per serving): farmed rainbow trout, 3 oz cooked: 645 IU; sockeye salmon, 3 oz cooked: 570 IU; one large egg: 44 IU ("Vitamin D is in the yolk"); white mushrooms exposed to UV light, ½ cup: 366 IU (vitamin D2); ordinary portabella mushrooms, ½ cup: 4 IU. source
• D2 versus D3: Tripkovic 2012 (meta-analysis) concluded that "vitamin D3 is more efficacious at raising serum 25(OH)D concentrations than is vitamin D2". The difference was significant with a bolus dose, "but the effect was lost with daily supplementation". The authors said effects "across age, sex, and ethnicity" could not be checked. source
• The 2016 global consensus states: "For daily treatment, both D2 and D3 are equally effective" and "When single large doses are used, D3 appears to be preferable compared to D2 because the former has a longer half-life." NIH ODS says the two forms "seem to have equivalent ability to cure rickets". source source 2
• Breast milk: NIH ODS states that "consumption of human milk alone does not ordinarily enable infants to meet vitamin D requirements, because it provides less than 0.6 to 2.0 mcg/L (25 to 78 IU/L)", and that the level depends on the mother's vitamin D status. CDC: "Breast milk alone does not provide infants with enough vitamin D." source source 2
• This guide's own arithmetic At the top of that range (78 IU per litre), a baby would need to drink more than 5 litres of breast milk a day to get 400 IU. source
• Mother's supplements: NIH ODS reports that breast milk from mothers taking at least 2,000 IU of D3 a day has higher levels, and CDC says families can discuss maternal high-dose supplements with a provider. The 2016 consensus recommends: "Lactating women should not take high amounts of vitamin D as a means of supplementing their infant." source source 2