Active form and Reservoir form of Vitamin D in Children with Acute Lower Respiratory Infections and Its Association with Severity of the Infection


Nirvana Tavahen 1 , Zahra Pourmoghaddas 2 , Behnoosh Esteki 1 , Nahid Aslani 1 , Hamid Rahimi 1 , *

1 Department of Pediatrics, Isfahan University of Medical Sciences, Isfahan, Iran

2 Child Growth and Development Research Center, Isfahan University of Medical Sciences, Isfahan, Iran

How to Cite: Tavahen N, Pourmoghaddas Z, Esteki B, Aslani N, Rahimi H. Active form and Reservoir form of Vitamin D in Children with Acute Lower Respiratory Infections and Its Association with Severity of the Infection, Arch Pediatr Infect Dis. 7(4): e83431. doi: 10.5812/pedinfect.83431.


Archives of Pediatric Infectious Diseases: 7 (4); e83431
Published Online: September 22, 2019
Article Type: Research Article
Received: August 18, 2018
Revised: July 27, 2019
Accepted: August 19, 2019


Background: Vitamin D plays an important role in regulating the immune system, calcium and phosphorus homeostasis, and bone formation. This micronutrient plays an important role in the incidence and severity of respiratory infections.

Objectives: The aim of this study was to evaluate the vitamin D serum level in children with acute lower respiratory infections (ALRIs) and its association with the severity of infection with vitamin D serum level.

Methods: This cross-sectional study was conducted on 99 children with ALRIs aged 20.13 ± 17.55 months who were selected with a simple random sampling technique. The children were examined and evaluated at the time of admission. Their data, including demographic characteristics and the findings of the physical examination and laboratory, were recorded in the questionnaires. Serum level of 1,25-dihydroxy vitamin D3 [1,25(OH)2D] and 25-hydroxyvitamin D3 [25(OH)D] were measured by HPLC method.

Results: children with severe acute lower respiratory infection had a significant lower level of 25(OH) D (P = 0.02). Indeed, data analysis showed a level of 25(OH) D inversely associated with severity of acute lower respiratory infections in children (B = -0.7, P = 0.00).

Conclusions: The severity of the lower respiratory tract infections was inversely proportional to the level of 25(OH)D, and it may be hoped that increasing 25(OH)D level may reduce the severity of ALRIs.

1. Background

Among infectious diseases, pneumonia is the leading cause of childhood mortality and the most common cause of hospitalization (1, 2). The mortality rate due to acute respiratory infections, especially pneumonia, is estimated to be two million per year, which is the highest in developing countries, including Iran (1). The WHO report indicates that ALRIs account for 19% of mortality in children under the age of five (3).

The global prevalence of vitamin D deficiency among children in different parts of the world is estimated to be between 30% and 90% depending on diet, environmental conditions, and latitude (4). In limited studies conducted in Iran, the prevalence of vitamin D deficiency in children has ranged from 81.3% and 37.9% based on age, gender, and living place (5-7), which is also linked to the amount and type of vitamin D intake.

Practically, 25(OH)D and 1,25(OH)2D are surrogate markers of reservoir and active forms of vitamin D, respectively. Although measuring serum level of 25(OH)D is generally considered the best way to determine the status of vitamin D in humans (8-10), 1,25(OH)2D has the ultimate role of vitamin D in the body, including in the immune system. Due to a relatively short half-life (12 to 36 hours) of 1,25(OH)2D compared to 25(OH)D (3 weeks) (11, 12), it is probably better to measure the serum level of 1,25(OH)2D instead of 25(OH)D for a better prediction of the vitamin D role in decreasing the severity and improving prognosis of patients with ALRIs.

Different studies have had different results regarding vitamin D deficiency and its effects on respiratory infections (13-17). Some studies have shown the potential protective effect of vitamin D against ALRIs (13, 15, 16), while other studies have shown that vitamin D supplementation to infants cannot prevent pneumonia (17).

Researches, which evaluate the association of 25(OH)D and severity of respiratory tract infection, are scarce and findings are controversial. One study conducted in Iran in 2016 - 2017 (18), declared a positive relationship between low level of 25(OH)D and severity of pneumonia. However, some studies found no such association, for example, the study of Kim et al., in a tertiary referral hospital in South Korea (19).

Confirming this argument, serum level of 1,25(OH)2D is associated with an increase in symptoms and mortality in patients with HIV infection, however, low 1,25(OH)2D levels did not appear to be related to vitamin D deficiency (20). Another study by Zittermann et al. showed that low serum levels of 1,25(OH)2D in patients with heart disease is associated with an increase in death due to coronary heart disease, heart failure, hypertension, diabetes, and renal failure (21). Powe et al. also recommended that both serum level of 1,25(OH)2D and 25(OH)D should be checked to understand the complex effects of vitamin D metabolism (22).

As far as we know, in our country, despite the low level of vitamin D, there have been few studies on the association of ALRIs with vitamin D level. To the best of our knowledge, this is the first study conducted to investigate the serum level of 25(OH)D and 1,25(OH)2D in children with ALRIs, simultaneously.

2. Objectives

Considering the importance of community-acquired pneumonia in terms of pathogenicity, mortality and its imposed costs, and the controversy about the role of vitamin D deficiency in ALRIs in children and the relation between the severity of the disease and vitamin D serum level, this study was conducted to simultaneously study the serum level of 25(OH)D and 1,25(OH)2D in children with ALRIs and its association with severity of disease.

3. Methods

The simple random sampling technique was used in this hospital-based cross-sectional study to select 110 children among children aged two months to five years admitted with fever, cough, and tachypnea to the Imam Hossein Children’s Hospital (the major tertiary referral hospital in Isfahan province, Iran). Parents’ consent for their children’s participation in the study was also considered as mandatory. The study was approved by the Ethics Committee of Isfahan University of Medical Sciences (≠396031). Patients excluded from the study were those with underlying medical disorders including: history of chronic pulmonary disease (such as CF, asthma, etc.), aspiration pneumonia, anatomical defects of airways or lungs, chronic kidney disease, swallowing disorder, congenital heart disease, gastroesophageal reflux, malabsorption, jaundice, neuromuscular disease (such as SMA, etc.), a known immunodeficiency disease, and a history of receiving drugs such as: Phenobarbital, phenytoin, carbamazepine, isoniazid, theophylline, rifampin.

Explaining the purpose of the study to parents and obtaining written consent from them, information and findings from the clinical history and the physical examination were listed in the designed checklist.

World health organization’s (WHO) definition of ALRIs was used for definition of ALRIs or pneumonia, i.e. cough or difficulty in breathing with fast breathing (≥ 50 breaths/min in a child aged two to 11 months or ≥ 40 breaths/min in a child aged one to five years or ≥ 30 breaths/min in a child aged > 5 years) or chest indrawing (23). Bronchiolitis was considered for children younger than two years old, with a viral upper respiratory tract prodrome, followed by increased respiratory effort and wheezing (24).

As there is no clinical diagnostic criterion for the definitive diagnosis of bacterial pneumonia, and a series of clinical manifestations and radiological findings are required for a definitive diagnosis (25), the diagnosis of bacterial pneumonia was based on the presence of consolidation, opacity, or infiltrate on a chest radiograph and standardized radiographic definition of pneumonia based on WHO criteria in children who have taken chest radiography (26-28). For the cases without chest radiography, a set of symptoms and laboratory findings were used to differentiate the two types of bacterial and viral pneumonia. These symptoms and findings included persistent or recurrent fever > 38.5°C, increased respiratory rate, chest indrawing, hypoxia, leukocytosis > 20,000, and neutrophilia, and most importantly, the clinical course of patients during admission and course of the disease (26, 29).

According to criteria provided by Seiden et al. and Dooley et al. the severity of infection in patients with pneumonia and bronchiolitis was classified in three categories: mild, moderate and severe (30, 31).

Population study weights and heights were measured with standard methods and WHO chart were used for interpretation.

To determine the serum level of 1,25(OH)2D and 25(OH)D in patients, 2 mL of the blood clot was collected in the test tube and sent to the lab. Sampling was performed either at the time of admission or at most within the first 24 hours of admission. The serum of patients was stored in a freezer at -20°C. Serum level of 1,25(OH)2D and 25(OH)D were measured by HPLC method using commercial kits (ZellBio GmbH, Germany), according to the manufacturer’s instructions.

We considered a serum level of 1,25(OH)2D and 25(OH) greater than or equal to 30 ng/mL as sufficient, the serum level of 21 - 29 ng/mL as deficient and serum level below 20 ng/mL as severely deficient.

The data were analyzed by SPSS software version 23 and analyzed with the significance level of 0.05. To describe the quantitative data, the mean and standard deviation were used. To characterize the qualitative data, a frequency index and frequency were used; we used variance analysis, chi-square, independent t-test. Also linear regression test was used for association of 1,25(OH)2D, 25(OH)D and severity of ALRIs

4. Results

Eleven out of 110 children involved in the study were excluded from the study, according to exclusion criteria, and the study continued with 99 children. Demographic data of children was presented in Table 1.

Table 1. Demographic Data, 1,25(OH)vitD, and 25(OH)D in the Population Studya,b
VariablesSeverity of ALRIsP Value
Mild to ModerateSevere
Age, mo20.33 ± 13.8019.73 ± 12.680.84
Female33 (80.5)8 (19.5)
Male40 (69)18 (31)
Gestational age, wk0.68
< 3225 (66.7)12 (33.3)
32 - 3636 (72)14 (28)
> 3614 (82.4)3 (17.6)
< 250017 (58.6)3 (17.6)
≥ 250017 (58.6)12 (41.4)
Day care centre attendance42 (72.4)16 (27.6)0.72
History of hospitalization due to pneumonia14 (51.9)13 (48.1)0.05
Vitamin D supplementation0.05
Never18 (60)12 (40)
Some times12 (66.71)6 (33.3)
Always43 (84.3)8 (15.7)
Socioeconomic status0.94
Low26 (72.2)10 (27.8)
Moderate39 (75)13 (25)
High8 (72.71)3 (25)
1,25(OH)vitD178.72 ± 77.8187.24 ± 65.650.57
25(OH)D39.26 ± 18.7828.42 ± 17.780.02

aValues are expressed as mean ± SD or No. (%).

bSocioeconomic status include: family income, mother education level, and number of family 1,25(OH)2D: 1,25-dihydroxyvitamin D3; 25(OH)D: 25-hydroxyvitamin D3, ALRIs: acute lower respiratory infections.

A total of 7% of children had a weight for height Z. score of ≤ -2.5, -3. None of children had severe malnutrition (Z. Score ≤ -3). The percentage of breastfeeding and formula feeding in the study group were 40.4 and 33.3, respectively and 26.2% of children were fed on both. Regarding vitamin D supplementation in the first two years of life, 51% of children had a sufficient intake, 18% had an insufficient intake, while 30% didn’t receive any vitamin D.

According to the findings, 36.4% (number = 36, male = 22, female = 14) of patients had bronchiolitis, 39% (number = 39, male = 18, female = 21) had viral pneumonia, and 24% (number = 24, male = 19, female = 24) had bacterial pneumonia.

Child with Bronchiolitis, viral pneumonia, and bacterial pneumonia had no significant difference in levels of 25(OH)D and 1, 25(OH)2D (Table 2).

Table 2. Levels of 25(OH) D and 1,25(OH)2D in Lower Respiratory Infections (ALRIs)a
Groups of ALRIsMean ± SDP Value
25(OH)DBronchiolitis39.55 ± 18.710.36
Bacterial pneumonia32.82 ± 18.60
Viral pneumonia35.23 ± 20.75
1,25(OH)2DBronchiolitis177.49 ± 10.360.24
Bacterial pneumonia176.03 ± 95.5
Viral pneumonia173.35 ± 89.14

a1,25(OH)2D: 1,25-dihydroxyvitamin D3; 25(OH)D: 25-hydroxyvitamin D3; ALRIs: acute lower respiratory infections.

T-test analysis showed child with lower level of 25(OH)D had significant sever ALRIs (P = 0.02) (Table 1).

Linear regression analysis showed a lower level of 25(OH)D significantly associated with severe lower respiratory syndromes (B = -0.7, P = 0.00), unlike, 1, 25(OH)D, which was not significantly associated with more severe ALRIs (B = -0.01. P = 0.99) (Table 3).

Table 3. Association of 25(OH)D and 1,25(OH)2D with Severity of Acute Lower Respiratory Infectionsa
BStandard ErrorP Value

a1,25(OH)2D: 1,25-dihydroxyvitamin D3; 25(OH)D: 25-hydroxyvitamin D3.

5. Discussion

According to data in the present study, low serum level of 25(OH)D was significantly correlated with increasing ALRIs severity.

In the review study conducted in 2014, 13 out of 18 studies revealed that vitamin D deficiency was common in children with respiratory infections, and in four other studies, there was no significant difference in vitamin D level between patients and control groups (9). The result of this study, which was conducted in a country with vitamin D deficiency is prevalent among children, which is in line with studies proving the positive effect of vitamin D deficiency in increasing the risk of pneumonia in children.

On the other hand, the serum level of active form of vitamin D [1,25(OH)2D] in children with a mild ALRIs was lower than severe cases. This difference was not statistically significant. While Pletz and colleagues found a modest positive relationship between serum level of 25(OH)D and 1,25(OH)2D in 300 adult patients with community-acquired pneumonia; only serum level of 1,25(OH)2D had a significant negative correlation with pneumonia severity (32). This difference may be due to confounding factors such as age (recent study was in adults) and other underlying conditions, however, there is no linear relationship between serum 25(OH)D level and serum level of 1,25(OH)2D in both studies, confirming the complexity of vitamin D metabolism and the need for further studies to determine the mechanism through which vitamin D affects the immune system.

According to the results of this study, low serum level of 25(OH)D has an effect on the increase of ALRIs severity. Pletz and colleagues found that gender and 25(OH)D level in adults with pneumonia were effective in increasing ALRIs (32). In this study, as in the study of Hosseininejad and colleagues, factors such as age, number of admissions due to pneumonia, and level of vitamin 1,25(OH)2D were considered ineffective (33).

In our study, there was neither a significant relationship between the severity of the infection and the type of nutrition nor between the degree of malnutrition and the length of hospitalization.

One study in Tanzania found that exclusive breastfeeding was associated with a significant decrease in the risk of respiratory disease in the first six months of life among 666 children (34). However, a cohort study from South Africa reported higher mortality in infants who were exclusively breast fed than in infants who were mixed fed (35). In our country and some other developing countries, ineffectiveness of breast feeding on severity of infections in infants may be due to vitamin D insufficiency in mothers. It also may be due to the fact that effectiveness of breast feeding on severity of infections, mostly seen in the first two years of age but target groups of our study, were children under five years old.

Factors unrelated to pneumonia severity may influence the hospitalization decision. However, studies in adults with pneumonia indicate that site of care decisions vary considerably by provider and that risk for severe outcomes is often overestimated (36).

In most studies, a significant relationship between FTT and severity of infections was found (37). However, we did not see this relationship, which may be due to low numbers of FTT cases in our study.

In this study, the decrease in serum level of 25(OH)D caused a significant increase in some ALRIs’ severity criteria such as ICU admission, decreased arterial oxygen saturation, prolonged capillary refill time, more duration of oxygen therapy, and more duration of hospitalization. These results are partially consistent with the results of Zhang et al. 2016 in China, confirming inverse correlation between serum level of 25(OH)D and ALRIs’ severity criteria in children with ALRIs such as respiratory rate, cyanosis, chest indrawing, feeding intolerance, and the need for oxygen (38). In 2007 and 2008 a Canadian study of children with ALRIs, had no significant difference between patients and control group regarding their vitamin D serum level, however, most of the children admitted to ICU with ALRIs were deficient in vitamin D (39). In the present study, decreasing serum level of 25(OH)D significantly increases the incidence of admission of children with ALRIs in ICU.

Although the findings of this study and most observational studies indicate a low serum level of 25(OH)D in children with pneumonia, the addition of vitamin D supplementation to children’s or adolescents’ diets in some cases does not reduce the incidence of respiratory infection. This may be due to several reasons. In most of these studies, the serum level of 25(OH)D have not been measured before the onset of supplementation, and presumably, the administration of vitamin D in people with normal serum level of vitamin D cannot help reduce the incidence of respiratory infections. On the other hand, the dose and mode of administration of vitamin D in these individuals have not been the same, and a universal protocol has not been determined in this case (40). However, in our study, we did not address the effect of vitamin D supplements on reducing the incidence and severity of ALRIs, but future studies are needed to be done on the effect of supplementation with vitamin D in reducing the incidence and severity of ALRIs, while serum level of both 1,25(OH)2D and 25(OH)D are measured in children before administering vitamin D.

The strengths of the present study are the use of valid criteria for the diagnosis and differentiation of ALRIs types and the assessment of the severity of ALRIs. In addition, this study, unlike the previous ones, has concurrently measured the level of reservoir form and active form of vitamin D in children with ALRIs to help clarify the role of vitamin D in the ALRIs.

One of the limitations of this study is lack of a healthy control group, and the other one is not checking the changes of serum level of reservoir form and active form of vitamin D before the onset of the ALRIs and in their courses.



  • 1.

    Paradisi F, Corti G. Antibiotic resistance in community-acquired pulmonary pathogens. Semin Respir Crit Care Med. 2000;21(1):33-43. doi: 10.1055/s-2000-9930. [PubMed: 16088716].

  • 2.

    Dean N. Treatment guidelines improve management of community-acquired pneumonia. Curr Treat Options Infect Dis. 2002;4:153-63.

  • 3.

    UNICEFS. State of Asia-Pacific's children 2008: Child survival. 2008.

  • 4.

    Arabi A, El Rassi R, El-Hajj Fuleihan G. Hypovitaminosis D in developing countries-prevalence, risk factors and outcomes. Nat Rev Endocrinol. 2010;6(10):550-61. doi: 10.1038/nrendo.2010.146. [PubMed: 20852586].

  • 5.

    Kelishadi R, Moeini R, Poursafa P, Farajian S, Yousefy H, Okhovat-Souraki AA. Independent association between air pollutants and vitamin D deficiency in young children in Isfahan, Iran. Paediatr Int Child Health. 2014;34(1):50-5. doi: 10.1179/2046905513Y.0000000080. [PubMed: 24090719].

  • 6.

    Habibesadat S, Ali K, Shabnam JM, Arash A. Prevalence of vitamin D deficiency and its related factors in children and adolescents living in North Khorasan, Iran. J Pediatr Endocrinol Metab. 2014;27(5-6):431-6. doi: 10.1515/jpem-2013-0198. [PubMed: 24519715].

  • 7.

    Saki F, Dabbaghmanesh MH, Omrani GR, Bakhshayeshkaram M. Vitamin D deficiency and its associated risk factors in children and adolescents in southern Iran. Public Health Nutr. 2017;20(10):1851-6. doi: 10.1017/S1368980015001925. [PubMed: 26051113].

  • 8.

    Holick MF. Vitamin D deficiency. N Engl J Med. 2007;357(3):266-81. doi: 10.1056/NEJMra070553. [PubMed: 17634462].

  • 9.

    Holick MF. Vitamin D: The underappreciated D-lightful hormone that is important for skeletal and cellular health. Curr Opin Endocrinol Diabetes Obes. 2002;9(1):87-98. doi: 10.1097/00060793-200202000-00011.

  • 10.

    Zittermann A. Vitamin D and disease prevention with special reference to cardiovascular disease. Prog Biophys Mol Biol. 2006;92(1):39-48. doi: 10.1016/j.pbiomolbio.2006.02.001. [PubMed: 16600341].

  • 11.

    Jongen MJ, Bishop JE, Cade C, Norman AW. Effect of dietary calcium, phosphate and vitamin D deprivation on the pharmacokinetics of 1,25-dihydroxyvitamin D3 in the rat. Horm Metab Res. 1987;19(10):481-5. doi: 10.1055/s-2007-1011858. [PubMed: 3428866].

  • 12.

    Mawer EB, Schaefer K, Lumb GA, Stanbury SW. The metabolism of isotopically labelled vitamin D3 in man: The influence of the state of vitamin D nutrition. Clin Sci. 1971;40(1):39-53. doi: 10.1042/cs0400039. [PubMed: 4321723].

  • 13.

    Ginde AA, Mansbach JM, Camargo CA Jr. Association between serum 25-hydroxyvitamin D level and upper respiratory tract infection in the Third National Health and Nutrition Examination Survey. Arch Intern Med. 2009;169(4):384-90. doi: 10.1001/archinternmed.2008.560. [PubMed: 19237723]. [PubMed Central: PMC3447082].

  • 14.

    Larkin A, Lassetter J. Vitamin D deficiency and acute lower respiratory infections in children younger than 5 years: Identification and treatment. J Pediatr Health Care. 2014;28(6):572-82. quiz 583-4. doi: 10.1016/j.pedhc.2014.08.013. [PubMed: 25441970].

  • 15.

    Bergman P, Lindh AU, Bjorkhem-Bergman L, Lindh JD. Vitamin D and respiratory tract infections: A systematic review and meta-analysis of randomized controlled trials. PLoS One. 2013;8(6). e65835. doi: 10.1371/journal.pone.0065835. [PubMed: 23840373]. [PubMed Central: PMC3686844].

  • 16.

    Charan J, Goyal JP, Saxena D, Yadav P. Vitamin D for prevention of respiratory tract infections: A systematic review and meta-analysis. J Pharmacol Pharmacother. 2012;3(4):300-3. doi: 10.4103/0976-500X.103685. [PubMed: 23326099]. [PubMed Central: PMC3543548].

  • 17.

    Manaseki-Holland S, Maroof Z, Bruce J, Mughal MZ, Masher MI, Bhutta ZA, et al. Effect on the incidence of pneumonia of vitamin D supplementation by quarterly bolus dose to infants in Kabul: a randomised controlled superiority trial. Lancet. 2012;379(9824):1419-27. doi: 10.1016/S0140-6736(11)61650-4. [PubMed: 22494826]. [PubMed Central: PMC3348565].

  • 18.

    Talebi F, Rasooli Nejad M, Yaseri M, Hadadi A. Association of vitamin D status with the severity and mortality of community-acquired pneumonia in Iran during 2016-2017: A prospective cohort study. Rep Biochem Mol Biol. 2019;8(1):85-90. [PubMed: 31334293]. [PubMed Central: PMC6590933].

  • 19.

    Kim HJ, Jang JG, Hong KS, Park JK, Choi EY. Relationship between serum vitamin D concentrations and clinical outcome of community-acquired pneumonia. Int J Tuberc Lung Dis. 2015;19(6):729-34. doi: 10.5588/ijtld.14.0696. [PubMed: 25946368].

  • 20.

    Haug C, Muller F, Aukrust P, Froland SS. Subnormal serum concentration of 1,25-vitamin D in human immunodeficiency virus infection: Correlation with degree of immune deficiency and survival. J Infect Dis. 1994;169(4):889-93. doi: 10.1093/infdis/169.4.889. [PubMed: 7907645].

  • 21.

    Zittermann A, Schleithoff SS, Frisch S, Gotting C, Kuhn J, Koertke H, et al. Circulating calcitriol concentrations and total mortality. Clin Chem. 2009;55(6):1163-70. doi: 10.1373/clinchem.2008.120006. [PubMed: 19359534].

  • 22.

    Powe CE, Evans MK, Wenger J, Zonderman AB, Berg AH, Nalls M, et al. Vitamin D-binding protein and vitamin D status of black Americans and white Americans. N Engl J Med. 2013;369(21):1991-2000. doi: 10.1056/NEJMoa1306357. [PubMed: 24256378]. [PubMed Central: PMC4030388].

  • 23.

    WHO Guidelines Approved by the Guidelines Review Committee. Pocket book of hospital care for children: guidelines for the management of common childhood illnesses. 2nd ed. Geneva: World Health Organization; 2013. eng.

  • 24.

    Ralston SL, Lieberthal AS, Meissner HC, Alverson BK, Baley JE, Gadomski AM, et al. Clinical practice guideline: The diagnosis, management, and prevention of bronchiolitis. Pediatrics. 2014;134(5):e1474-502. doi: 10.1542/peds.2014-2742. [PubMed: 25349312].

  • 25.

    Rambaud-Althaus C, Althaus F, Genton B, D'Acremont V. Clinical features for diagnosis of pneumonia in children younger than 5 years: A systematic review and meta-analysis. Lancet Infect Dis. 2015;15(4):439-50. doi: 10.1016/S1473-3099(15)70017-4. [PubMed: 25769269].

  • 26.

    British Thoracic Society of Standards of Care Committee. BTS guidelines for the management of community acquired pneumonia in childhood. Thorax. 2002;57(Supplement 1):i1-i24. doi: 10.1136/thx.57.suppl_1.i1.

  • 27.

    Bradley JS, Byington CL, Shah SS, Alverson B, Carter ER, Harrison C, et al. Executive summary: The management of community-acquired pneumonia in infants and children older than 3 months of age: clinical practice guidelines by the Pediatric Infectious Diseases Society and the Infectious Diseases Society of America. Clin Infect Dis. 2011;53(7):617-30. doi: 10.1093/cid/cir625. [PubMed: 21890766]. [PubMed Central: PMC3202323].

  • 28.

    Cherian T, Mulholland EK, Carlin JB, Ostensen H, Amin R, de Campo M, et al. Standardized interpretation of paediatric chest radiographs for the diagnosis of pneumonia in epidemiological studies. Bull World Health Organ. 2005;83(5):353-9. [PubMed: 15976876]. [PubMed Central: PMC2626240].

  • 29.

    Shah SN, Bachur RG, Simel DL, Neuman MI. does this child have pneumonia?: The rational clinical examination systematic review. JAMA. 2017;318(5):462-71. doi: 10.1001/jama.2017.9039. [PubMed: 28763554].

  • 30.

    Dooley SR, Rodio B, Tyler L, Zorc J. Bronchiolitis. In: Bachur RG, Shaw KN, editors. Fleisher & Ludwig's textbook of pediatric emergency medicine. Lippincott Williams & Wilkins; 2015.

  • 31.

    Seiden J, Callahan JM. Pneumonia, community-acquired. In: Bachur RG, Shaw KN, editors. Fleisher & Ludwig's textbook of pediatric emergency medicine. Lippincott Williams & Wilkins; 2015.

  • 32.

    Pletz MW, Terkamp C, Schumacher U, Rohde G, Schutte H, Welte T, et al. Vitamin D deficiency in community-acquired pneumonia: Low levels of 1,25(OH)2 D are associated with disease severity. Respir Res. 2014;15:53. doi: 10.1186/1465-9921-15-53. [PubMed: 24766747]. [PubMed Central: PMC4046524].

  • 33.

    Hosseininejad N, Kalbasi Z, Afshar J. [Vitamin D and childhood pneumonia]. Razi J Med Sci. 2016;22(140):109-16. Persian.

  • 34.

    Mwiru RS, Spiegelman D, Duggan C, Peterson K, Liu E, Msamanga G, et al. Relationship of exclusive breast-feeding to infections and growth of Tanzanian children born to HIV-infected women. Public Health Nutr. 2011;14(7):1251-8. doi: 10.1017/S136898001000306X. [PubMed: 21324223]. [PubMed Central: PMC3366264].

  • 35.

    Bobat R, Moodley D, Coutsoudis A, Coovadia H. Breastfeeding by HIV-1-infected women and outcome in their infants: A cohort study from Durban, South Africa. AIDS. 1997;11(13):1627-33. doi: 10.1097/00002030-199713000-00012. [PubMed: 9365768].

  • 36.

    Fine MJ, Hough LJ, Medsger AR, Li YH, Ricci EM, Singer DE, et al. The hospital admission decision for patients with community-acquired pneumonia. Results from the pneumonia Patient Outcomes Research Team cohort study. Arch Intern Med. 1997;157(1):36-44. doi: 10.1001/archinte.1997.00440220051007. [PubMed: 8996039].

  • 37.

    Miller TL, Easley KA, Zhang W, Orav EJ, Bier DM, Luder E, et al. Maternal and infant factors associated with failure to thrive in children with vertically transmitted human immunodeficiency virus-1 infection: The prospective, P2C2 human immunodeficiency virus multicenter study. Pediatrics. 2001;108(6):1287-96. doi: 10.1542/peds.108.6.1287. [PubMed: 11731650]. [PubMed Central: PMC4383837].

  • 38.

    Zhang X, Ding F, Li H, Zhao W, Jing H, Yan Y, et al. Low serum levels of vitamins A, D, and E are associated with recurrent respiratory tract infections in children living in Northern China: A case control study. PLoS One. 2016;11(12). e0167689. doi: 10.1371/journal.pone.0167689. [PubMed: 27936124]. [PubMed Central: PMC5147939].

  • 39.

    McNally JD, Leis K, Matheson LA, Karuananyake C, Sankaran K, Rosenberg AM. Vitamin D deficiency in young children with severe acute lower respiratory infection. Pediatr Pulmonol. 2009;44(10):981-8. doi: 10.1002/ppul.21089. [PubMed: 19746437].

  • 40.

    Bryson KJ, Nash AA, Norval M. Does vitamin D protect against respiratory viral infections? Epidemiol Infect. 2014;142(9):1789-801. doi: 10.1017/S0950268814000193. [PubMed: 25030183].

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