Vaccination timeliness and completeness among preterm and low birthweight infants: a national cohort study

Figures & data

Figure 1. Scatter plot for birth week and birthweight

Note: A strong correlation was found between birth week and birthweight, with a Pearson Correlation coefficient r = 0.621.

Table 1. General characteristics of the 2016 birth cohort, Israel

Characteristics	Total (n = 181,543)
Gender, No. (%)
Male	93,434 (51.5)
Female	88,109 (48.5)
Birthweight – categorical, No. (%)
$\ge$2500 g	167,647 (92.3)
2000–2499 g	9,661 (5.3)
1500–1999 g	2,629 (1.4)
1000–1499 g	1025 (0.6)
$<$1000 g	580 (0.3)
Birthweight – continuous (gram)
Mean [SD]	3200.0 [530.0]
Median [IQR]	3240.0 [2920.0–3550.0]
Gestational age at birth (weeks)
Mean [SD]	39.0 [1.9]
Median [IQR]	39.0 [38.0–40.0]
Gestational age at birth – categorical, No. (%)
$\ge$37 weeks	168,835 (93.0)
32–36 weeks	11,074 (6.1)
28–31 weeks	1,089 (0.6)
$<$ 28 weeks	545 (0.3)
Birth order – categorical, No. (%)
First born	51,870 (28.6)
Second born	49,060 (27.0)
Third born	35,845 (19.7)
Fourth born and above	44.768 (24.7)
Number of children – categorical, No. (%)
Singleton	173,737 (95.7)
Multiple	7,806 (4.3)
Ethnicity, No. (%)
Jews & Others	140,233 (77.2)
Arabs	41,310 (22.8)
Socioeconomic rank (1–10)
Rank 1–3	77,451 (42.7%)
Rank 4–7	73,748 (40.6%)
Rank 8–10	30,344 (16.7%)
Month of birth, categorical, No. (%)
January–March	44,618 (24.6)
April–June	42,856 (23.6)
July–September	47,752 (26.3)
October–December	46,317 (25.5)
Length of hospital stay, categorical, No. (%)
1–6 d	171, 313 (94.4)
7–29 d	8,097 (4.5%)
30 d or more	2133 (1.2%)

Abbreviations: SD, standard deviation; IQR, interquartile range.

Figure 2. Cumulative proportion of first dose of DTaP-IPV-Hib vaccine uptake by child’s age in days in NBW and LBW children born in 2016 and followed up to 24 months, Israel

Note: The curves show the cumulative proportion of children vaccinated for first dose of DTaP-IPV-Hib over time. The vertical lines represent the day at which vaccination uptake reached 90% and 95% within each age group.

Figure 3. Distribution of vaccination timing by defined categories (status at the age of 24 months) for selected vaccine doses, in children born in Israel, 2016

Abbreviations: DTaP-IPV-Hib 1, diphtheria, tetanus, acellular pertussis, polio, Haemophilus influenzae B vaccine, first dose.

Figure 4. Forest plot presenting OR for risk of vaccination delay among NBW and LBW infants

Note: In early infancy LBW children are at a higher risk of vaccination delay (vaccine dose administered more than 30 d after required age), compared to NBW weight. The risk for later doses within each series is generally lower as doses progress. In some cases, vaccinations administered at older ages and not limited by earlier doses from a series show an advantage among LBW infants. Abbreviations: NBW, normal birthweight (≥2500 g); LBW, low birthweight (<2500 g).

Table 2. Multiple logistic regression model, dependent variable – DTaP-IPV-Hib 1 – age-appropriate vaccination status.^a

Variables	Birthweight – main independent variable Adjusted OR [95% CI]	Gestational age – main independent variable Adjusted OR [95% CI]
Gender
Male	1.06 [1.02–1.10] *	1.06 [1.03–1.10] *
Female	reference	reference
Mother family status
Married	reference	reference
Other	1.54 [1.44–1.65] *	1.54 [1.44–1.65] *
Ethnicity
Jew & others	3.27 [3.07–3.48] *	3.30 [3.10–3.52] *
Arab	reference	reference
Birthweight
$\ge$2500 g	reference	Na
2000–2500 g	0.98 [0.90–1.07]	Na
1500–2000 g	1.56 [1.36–1.78] *	Na
1000–1500 g	3.34 [2.81–3.96] *	Na
$<$1000 g	17.03 [13.58–21.35] *	Na
Gestational age at birth
$\ge$37 weeks	Na	reference
32–36 weeks	Na	1.10 [1.02–1.19] *
28–32 weeks	Na	3.62 [3.08–4.27] *
$<$ 28 weeks	Na	21.77 [16.98–27.91] *
Birth order
First born	reference	reference
Second born	1.75 [1.65–1.85] *	1.77 [1.67–1.87] *
Third born	2.02 [1.90–2.14] *	2.02 [1.91–2.15] *
Fourth born and above	3.22 [3.04–3.40] *	3.25 [3.08–3.44] *
Socioeconomic rank
Rank 1–3	1.30 [1.23–1.37] *	1.31 [1.24–1.39] *
Rank 4–7	0.56 [0.53–0.59] *	0.56 [0.53–0.59] *
Rank 8–10	reference	reference
Month of birth
January–March	reference	reference
April–June	0.91 [0.87–0.96] *	0.91 [0.87–0.96] *
July–September	1.11 [1.06–1.17] *	1.11 [1.06–1.17] *
October–December	0.93 [0.89–0.98] *	0.93 [0.88–0.98] *

*p-value $\le$<0.001.

^aThe OR in the regression is defined as the rate of delayed initiation of the DTaP-IPV-Hib 1 vaccine.