Is there a recommended vitamin A dose for 7 month old babies in some countries? Is it good to have a Vitamin A supplementation at that age? I heard too much vitamin A is not good during pregnancy, but I am not sure how about the first year of the baby.
Please see the full text of the review by Imdad et al (2017) for the benefits and side effects of the supplementation.
This review (and my answer) does not address recommendations for areas without vitamin A deficiency.
Note that giving too much vitamin A can be harmful (Hypervitaminosis A).
Therefore, like any supplement, vitamin A supplements should generally only be given if there is a risk of vitamin A deficiency, which depends on the child's health and nutrition - in particular, vitamin A deficiency is rare in developed countries.
Please consult a medical or nutrition professional before deciding to give supplements.
Is it good to have a Vitamin A supplementation at that age?
Whether it is "good" or not, depends on the specific case.
In areas with significant Vitamin A deficiency, supplementation is beneficial:
Vitamin A supplementation is associated with a clinically meaningful reduction in morbidity and mortality in children.
There are general recommendations for some countries, or, more exactly, areas with vitamin A deficiency (VAD). For example, see: World Health Organization (2011) Vitamin A supplementation for infants and children 6-59 months of age: https://www.who.int/nutrition/publications/micronutrients/guidelines/vas_6to59_months/en/
According to a more recent Cochrane review of 47 studies across 19 countries (Imdad et al., 2017), for 7 month-old children living in areas with vitamin A deficiency, the recommended vitamin A dose is 100,000 IU every six months.
Imdad A, Mayo-Wilson E, Herzer K, Bhutta ZA. Vitamin A supplementation for preventing morbidity and mortality in children from six months to five years of age. Cochrane Database of Systematic Reviews 2017, Issue 3. Art. No.: CD008524. DOI: 10.1002/14651858.CD008524.pub3 : https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD008524.pub3/full
Again, please see the full text of the review for the benefits and side effects (added in bold) of the supplementation. And, again, this review (and my answer) does not address recommendations for areas without vitamin A deficiency.
The World Health Organization (WHO) currently recommends [vitamin A supplementation (VAS)] to children between 6 and 59 months of age, in a dose of 100,000 IU for children aged 6 to 12 months and a dose of 200,000 IU for children aged one to five years, every six months. Based on updated results, we suggest continuing this policy for children under five years of age in areas at risk of [vitamin A deficiency (VAD)]. However, the global policy for universal VAS must be revisited for populations where VAD no longer remains a public health issue and VAD-associated deaths have markedly declined (Stevens 2015). [...]
(from the abstract:)
A meta-analysis for all-cause mortality included 19 trials (1,202,382 children). At longest follow-up, there was a 12% observed reduction in the risk of all-cause mortality for vitamin A compared with control using a fixed-effect model (risk ratio (RR) 0.88, 95% confidence interval (CI) 0.83 to 0.93; high-quality evidence). [...] Nine trials reported mortality due to diarrhoea and showed a 12% overall reduction for VAS (RR 0.88, 95% CI 0.79 to 0.98; 1,098,538 participants; high-quality evidence). There was no significant effect for VAS on mortality due to measles, respiratory disease, and meningitis. VAS reduced incidence of diarrhoea (RR 0.85, 95% CI 0.82 to 0.87; 15 studies; 77,946 participants; low-quality evidence) and measles (RR 0.50, 95% CI 0.37 to 0.67; 6 studies; 19,566 participants; moderate-quality evidence). However, there was no significant effect on incidence of respiratory disease or hospitalisations due to diarrhoea or pneumonia. There was an increased risk of vomiting within the first 48 hours of VAS (RR 1.97, 95% CI 1.44 to 2.69; 4 studies; 10,541 participants; moderate-quality evidence).
Vitamin A supplementation is associated with a clinically meaningful reduction in morbidity and mortality in children. Therefore, we suggest maintaining the policy of universal supplementation for children under five years of age in populations at risk of VAD.
Imdad, A., Yakoob, M.Y., Sudfeld, C. et al. Impact of vitamin A supplementation on infant and childhood mortality. BMC Public Health 11, S20 (2011) doi:10.1186/1471-2458-11-S3-S20 : https://bmcpublichealth.biomedcentral.com/articles/10.1186/1471-2458-11-S3-S20
Map of areas with vitamin A deficiency: https://bmcpublichealth.biomedcentral.com/articles/10.1186/1471-2458-11-S3-S20/figures/13
American Academy of Pediatrics ( https://www.aap.org/ ) has no recommendations on vitamin A supplementation for children that I could find at the time of writing (compare this to well-known and publicized recommendations for vitamin D supplementation)
"vitamin A" site:https://www.aap.org: https://www.google.com/search?q=%22vitamin+A%22+site%3Ahttps%3A%2F%2Fwww.aap.org
"vitamin D" site:https://www.aap.org: https://www.google.com/search?q=%22vitamin+D%22+site%3Ahttps%3A%2F%2Fwww.aap.org
National Institutes of Health (NIH) Office of Dietary Supplements (ODS) is rather terse regarding vitamin A supplementation in the United States and other developing countries, see: NIH ODS, Vitamin A: Fact Sheet for Health Professionals, October 11, 2019: https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/ :
Frank vitamin A deficiency is rare in the United States. However, vitamin A deficiency is common in many developing countries, often because residents have limited access to foods containing preformed vitamin A from animal-based food sources and they do not commonly consume available foods containing beta-carotene due to poverty. [...]
In developed countries, clinical vitamin A deficiency is rare in infants and occurs only in those with malabsorption disorders. However, preterm infants do not have adequate liver stores of vitamin A at birth and their plasma concentrations of retinol often remain low throughout the first year of life. Preterm infants with vitamin A deficiency have an increased risk of eye, chronic lung, and gastrointestinal diseases. [...]
(In other words, again, vitamin A supplementation should be case-dependent and under supervision of a medical professional)
The federal government's 2015-2020 Dietary Guidelines for Americans notes that "Nutritional needs should be met primarily from foods. ... Foods in nutrient-dense forms contain essential vitamins and minerals and also dietary fiber and other naturally occurring substances that may have positive health effects. In some cases, fortified foods and dietary supplements may be useful in providing one or more nutrients that otherwise may be consumed in less-than-recommended amounts."