# Individual and familial factors associated with mRNA COVID-19 vaccine uptake in pregnancy: A large-scale registry-based linkage study

Jovan Elyass, Anteneh Desalegn, Nhung T H Trinh, Saima Orangzeb, Mahmoud Zidan, Hedvig Nordeng, Angela Lupattelli

<figure><img src="image_1.png" /></figure>

## To cite this version:

Jovan Elyass, Anteneh Desalegn, Nhung T H Trinh, Saima Orangzeb, Mahmoud Zidan, et al.. Individual and familial factors associated with mRNA COVID-19 vaccine uptake in pregnancy: A large-scale registry-based linkage study. Vaccine, 2024, 42 (21), pp.126171. 10.1016/j.vaccine.2024.126171. hal-04788261

HAL Id: hal-04788261

https://hal.science/hal-04788261v1

Submitted on 18 Nov 2024

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

<figure><img src="image_2.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
<figure><img src="image_3.png" /></figure>

# Individual and familial factors associated with mRNA COVID-19 vaccine uptake in pregnancy: A large-scale registry-based linkage study

Jovan Elyass<sup>a,b</sup>, Anteneh Desalegn<sup>a</sup>, Nhung T.H. Trinh<sup>a</sup>, Saima Orangzeb<sup>a</sup>, Mahmoud Zidan<sup>a</sup>, Hedvig Nordeng<sup>a,c</sup>, Angela Lupattelli<sup>a,*</sup>

<figure><img src="image_4.png" /></figure>

## ARTICLE INFO

**Keywords:**

mRNA COVID-19 vaccine

Pregnancy

Prenatal vaccine uptake

Paternal vaccination

## ABSTRACT

The association between maternal COVID-19 vaccination in pregnancy and factors such as high risk for severe COVID-19, pre-existing asthma, prior adverse reproductive history, or paternal COVID-19 vaccination during pregnancy, remains unclear. The aim of this study is two-fold: (i) to describe uptake of COVID-19 vaccine during pregnancy by maternal risk for severe COVID-19 and asthma, and (ii) to comprehensively examine individual and familial factors associated with vaccine uptake during pregnancy in Norway. Based on nation-wide registry-linkage data in Norway, we included 101,659 deliveries with gestational length ≥12 weeks, in 2021–2022. Our outcome measure was uptake of at least one dose of mRNA COVID-19 vaccine during pregnancy, using a narrow (first ever dose) and broad (any dose) definition. We fit univariate and multivariate modified Poisson regression models, clustered by county of residency and adjusted for calendar time, to estimate risk ratios (RR) with 95 % Confidence Intervals (CIs). Gestational uptake of any COVID-19 vaccine dose increased from <1 % before mid Aug-2021, to 38.8 % in the rest of 2021, and 48.9 % in 2022. Only 28.8 % and 33.9 % pregnant individuals with high risk for severe COVID-19 or asthma, respectively, received at least one COVID-19 vaccine dose. Paternal COVID-19 vaccination was strongly associated with greater vaccine uptake by pregnant individuals (adjusted RR: 7.2, 95 % CI: 6.8–7.5). Maternal SARS-CoV-2 infection pre-pregnancy (adjusted RR: 0.31, 95 % CI: 0.26, 0.37), familial and individual migrant status were associated with a considerable decreased likelihood of vaccine uptake in pregnancy. History of miscarriage or pregnancy with congenital anomaly were not associated with vaccine uptake. Despite rising COVID-19 vaccine rates in pregnancy, uptake remained low for high-risk individuals. Paternal vaccination, pre-pregnancy infection, migration status, and maternal citizenship were strongly associated with prenatal vaccine uptake. This knowledge can inform tailoring of future vaccination campaigns.

## 1. Introduction

Pregnant individuals have substantial higher risk of severe COVID-19 and death than non-pregnant counterparts, primarily if unvaccinated [1–4]. Prenatal SARS-CoV-2 infection also increases the risk of multiple adverse pregnancy and child outcomes [5–10]. With emerging reassuring data about the safety of mRNA COVID-19 vaccine in pregnancy [11], there is consensus that the benefit of prenatal vaccination outweighs any potential risk to both mother and child [12].

In Norway, adults of childbearing age working as healthcare professionals or having conditions associated with high risk of severe

COVID-19 illness were prioritized for COVID-19 vaccination in the beginning of 2021 [13]. In May 2021, all people aged 18–24 or 40–44 years were offered the first COVID-19 vaccine dose, and individuals in the age band 25–39 years came next in the national vaccination roll-out [13]. In Norway, the vaccination coverage with at least one dose of the COVID-19 vaccine was high among people of fertile age (88–92 %) during 2021 [14,15].

When it comes to pregnant individuals, national health authorities and professional medical organizations worldwide started recommending mRNA COVID-19 vaccination in this population, approximately in the second half of 2021 [12,16–18]. In August 2021, the Norwegian

<footnote><sup>a</sup> PharmacoEpidemiology and Drug Safety Research Group, Department of Pharmacy, Faculty of Mathematics and Natural Sciences, University of Oslo, Oslo, Norway</footnote>

<footnote><sup>b</sup> Université Bordeaux, INSERM, Bordeaux Population Health, Bordeaux, France</footnote>

<footnote><sup>c</sup> Department of Child Health and Development, Norwegian Institute of Public Health, Oslo, Norway</footnote>

<footnote>* Corresponding author at: University of Oslo, Faculty of Mathematics and Natural Sciences, Department of Pharmacy, 0316 Oslo, Norway.</footnote>

<footnote>E-mail address: angela.lupattelli@farmasi.uio.no (A. Lupattelli).</footnote>
authorities recommended mRNA COVID-19 vaccination during the second and third trimesters, while for the first trimester, the risk of severe illness in the woman or of high exposure to the virus had to be considered. By January 2022, vaccination was recommended at any trimester [19]. Although COVID-19 vaccination in pregnancy has increased following these recommendations, including in Norway [20], low uptake remains a challenge in individuals with lower education or younger age, living alone, and with migrant background [20–23]. In addition, the extent of vaccine uptake among pregnant individuals with underlying health risk for severe COVID-19, remains insufficiently studied [24].

Studying vaccine uptake in pregnancy only in relation to maternal sociodemographic and broadly defined migrant status, is insufficient for informing targeted vaccination campaigns and clinical counselling. Multiple studies have confirmed that lack of knowledge [25], unrealistic risk perceptions [26], and fear of adverse vaccine effects on the child are major drivers of COVID-19 vaccine hesitancy among pregnant individuals [27–29]. Yet, the role of adverse reproductive history and prior lived experience of poorer delivery outcomes is unclear. Because having a family member vaccinated against COVID-19 is related to lower vaccine hesitancy in pregnant individuals [24], understanding the specific contribution of paternal COVID-19 vaccination is critical.

The aim of this study is two-fold: (i) to describe the uptake of mRNA COVID-19 vaccine during pregnancy in Norway during a two-years' time span and according to maternal risk for severe COVID-19 and asthma; (ii) to examine the association of a broad set of individual and familial factors, including prior adverse pregnancy outcomes and paternal COVID-19 vaccination, with vaccine uptake during pregnancy. mRNA COVID-19 vaccine (hereafter, COVID-19 vaccine) uptake was examined as receipt of any dose (broad definition) and as first ever dose (narrow definition) during pregnancy.

# 2. Materials and methods

## 2.1. Data sources

This study is based on data from Medical Birth Registry of Norway (MBRN), the Norwegian Immunisation Registry (SYSVAK), the Norwegian Surveillance System for Communicable Diseases (MSIS), Statistics Norway (SSB), the Population Registry, the Norwegian Control and Payment of Health Reimbursements Database (KUHR), and the Norwegian Patient Registry (NPR). Linkage across these registries were facilitated using unique personal identification numbers.

The MBRN is a population-based registry containing information on all births in Norway since 1967 [30]. It is based on mandatory notification of all pregnancies lasting more than 12 weeks and contains various information on both mother and infant(s). The SYSVAK is a national electronic immunisation register based on mandatory records of individual vaccination since birth and includes the specific code and name of each vaccine, and date of vaccination [31]. The MSIS includes mandatory records of all polymerase chain reaction (PCR) SARS-CoV-2 tests and their results based on reports from municipal health officers and laboratories. SSB is a central agency that provides official statistics, including demographics, housing conditions, education and income [32]. The Population Registry collects information about residents in Norway and their citizenships. The KUHR provides comprehensive records of medical diagnoses given in primary and secondary outpatient care; the diagnosis classification follows the International Classification of Diseases, version 10 (ICD-10) and the International Classification of Primary Care (ICPC-2/ICPC-2B). The NPR contains information on specialist outpatient and inpatient care, and diagnostic codes follow the ICD-10 classification [33].

## 2.2. Study population

We included all singleton pregnancies with gestational length greater

than 12 weeks as registered in the MBRN with delivery date between 1-Jan-2021 and 31-Dec-2022. We excluded records with missing maternal identification number or missing gestational age, and individuals who received a non-RNA COVID-19 vaccine (see Fig. S1). The latter exclusion criterion was applied since the mRNA based vaccines by Pfizer-BioNTech and Moderna were those administered in the national vaccine roll-out [13]. To achieve the final study population for examining first dose vaccine uptake during pregnancy, we further excluded individuals with uptake of at least one mRNA COVID-19 vaccine pre-pregnancy start (n = 12,951).

## 2.3. COVID-19 vaccine uptake

Vaccine uptake during pregnancy was defined as receipt of at least one dose (broad definition) and as first ever dose (narrow definition) of any mRNA COVID-19 vaccine, as recorded in the SYSVAK, between the estimated last menstrual period date (LMP) and date of delivery. The LMP date was calculated by subtracting gestational length in days, ascertained via ultrasound, from the date of delivery. We did not consider non-mRNA COVID-19 vaccines as these were not primarily used in the vaccination program in Norway.

## 2.4. Individual and familial factors

We examined three sets of individual and familial factors, as described in detail in Table S1: (i) sociodemographic and life-style characteristics; (ii) maternal health, vaccination, and reproductive history; (iii) familial migration status and paternal COVID-19 vaccination. Maternal sociodemographic and life-style factors included: age, parity, marital and employment status, body mass index (BMI) at pregnancy start, and smoking before pregnancy, as ascertained in the MBRN. The SSB provided information on maternal educational level. Maternal health, vaccination and reproductive history included pre-existing epilepsy, whether the pregnancy was secondary to in-vitro fertility treatment (as ascertained in the MBRN), human-papilloma virus (HPV) and influenza vaccination within the past 10 years, as well as influenza vaccination in prior pregnancy. We defined pregnant individuals as having “low”, “moderate” or “high” risk for severe COVID-19 according to the Norwegian Institute of Public Health (NIPH) classification for vaccine prioritization [34]. The definition is based on diagnosis codes from the NPR and KUHR with a look-back period of five years before LMP (see Table S2). Asthma was not included in the risk grouping as done by the NIPH, but considered as separate factor, due to the inability of identifying uncontrolled asthma. The MBRN provided information on maternal history of pregnancy loss (miscarriage or stillbirth), prior foetus/child with any major congenital anomaly, prior caesarean section, or premature delivery in the past 10 years. Familial factors included paternal COVID-19 vaccination during the pregnancy window, parental migration status, and granular information about maternal primary citizenship (grouped into regions). We separately examined associations with SARS-CoV-2 infection, defined as at least one positive PCR test in the MSIS during the six months before LMP.

Up to 36.5 % of observations had missing data on at least one of the examined factors, mainly maternal occupation, education, and smoking status. Incomplete data on prior pregnancy outcomes and reproductive history, occupation, education, smoking status, paternal age, and migration status, were imputed using multiple imputation with chained equation (ten replications), assuming data were missing at random. The imputation model included vaccine, sociodemographic- and health-related variables [35,36].

## 2.5. Statistical analyses

We conducted descriptive statistics and then three sets of forward stepwise modified Poisson regression models, clustered by the individual's county of residency and adjusted by calendar time of delivery,
with COVID-19 vaccine uptake as binary outcome variable. We fit separate models for the narrow and broad definition of vaccine uptake during pregnancy [37,38]. In the former analysis, individuals with at least one dose of COVID-19 vaccine pre-pregnancy were excluded. We assessed separately (i) sociodemographic and life-style characteristics; (ii) maternal health, vaccination and reproductive history; and (iii) familial migration status and paternal COVID-19 vaccination, to avoid multicollinearity and to better distinguish the role of each variable set. Candidate variables were first selected based on a p-value of <0.20 in the univariable regression model. Selected variables were then included in a unique multivariable model, and variables with no role (p > 0.05) or yielding a change less than 20 % in the beta coefficients of the retained variables were removed [37]. The final multiple regression model included only statistically significant factors and those influencing substantially the effect estimate of the retained factors [37]. Associations with SARS-CoV-2 infection pre-pregnancy were examined separately, and the multivariable regression models were adjusted for maternal education and age. Results are presented as risk ratios (RR) with the corresponding 95 % Confidence Intervals (CI) for each factor examined. Data analyses was performed using STATA MP v.18.

In sub-analyses, we replicated the regression models separately in pregnancies with delivery date before and after the 18-Aug-2021, to appraise whether factors were consistently associated with any dose vaccine uptake before and after the favourable national recommendation of vaccination in pregnancy. The date 18-Aug-2021 marks major revisions in national recommendations favouring COVID-19 vaccination during 2nd and 3rd trimesters, as well as 1st trimester if the benefit outweighs the risks [18]. To better appraise the associations of prior pregnancy outcomes with vaccine uptake by parity, we replicated the regression model of “Maternal health, vaccination, and reproductive history” factors among multiparous pregnancies.

## 3. Results

The study population included 101,659 pregnant individuals with delivery date between 1-Jan-2021 through 31-Dec-2022 (Fig. S1), whereof 30.0 % (30,518/101,659) received at least one dose of the COVID-19 vaccine during pregnancy. Of the 30,518 individuals who received COVID-19 vaccine during pregnancy, 41.4 % (12,951/30,518) had received at least one dose pre-pregnancy (Table S3). Among those individuals with no COVID-19 vaccination pre-pregnancy, 19.8 % (17,567/88,708) had uptake of their first dose of the COVID-19 vaccine specifically during gestation. Most pregnant individuals had one (15,164/30,518: 49.7 %) or two (14,474/30,518: 47.4 %) cumulative doses taken specifically during gestation (Table S3).

Fig. S2 shows vaccine uptake by calendar time and date of delivery. Before 18-Aug-2021, vaccine uptake in pregnancy was 0.9 % and mainly in the third trimester (92.0 % of vaccinations). This proportion increased to 38.8 % in the rest of 2021 and to 48.9 % in 2022 (Table S4). In 2021, any dose vaccine uptake generally coincided with first dose uptake, but not in 2022 (Table S4). Overall, the gestational timing of any dose vaccine uptake was 32.1 % (n = 9,780) in the first trimester, 57.2 % (n = 17,442) in the second, and 35.9 % (n = 10,947) in the third trimester.

Table 1 shows the distribution of baseline individual and familial factors by any and first dose COVID-19 vaccine uptake during pregnancy. As shown in Table 2, only 28.8 % and 13.8 % of pregnant individuals with high risk for severe COVID-19 received respectively any dose or the first vaccine dose during gestation. Vaccine uptake was about 2–4 % higher in women with pre-existing asthma than in their counterpart.

Fig. 1 shows which factors among sociodemographic and life-style characteristics (Panels A-B), and maternal health, vaccination, and reproductive history (Panels C-D) were associated with any dose and first dose vaccine uptake during pregnancy. Fig. 2 shows associations with familial migration status and paternal COVID-19 vaccination. Results of the univariate analyses are shown in Tables S5 and S6. Lower

<caption>**Table 1**</caption>

Baseline characteristics by mRNA COVID-19 vaccine uptake during pregnancy, as any dose and first dose uptake. Numbers are presented as n with % unless otherwise specified.

<table><thead><tr><th rowspan="2"></th><th colspan="2">Vaccine uptake during pregnancy, any dose</th><th colspan="2">Vaccine uptake during pregnancy, first dose*</th></tr><tr><th>No<br>N = 71,141</th><th>Yes<br>N = 30,518</th><th>Yes<br>N = 17,567</th><th></th></tr></thead><tbody><tr><td colspan="5"><strong>Sociodemographic and life-style characteristics</strong></td></tr><tr><td>Maternal age in years; mean &amp; SD</td><td>30.9</td><td>4.7</td><td>31.5</td><td>4.5</td></tr><tr><td>Nulliparous (yes)</td><td>29,721</td><td>41.8</td><td>13,609</td><td>44.6</td></tr><tr><td>Married/cohabiting (yes)</td><td>66,790</td><td>93.9</td><td>29,131</td><td>95.5</td></tr><tr><td>Missing</td><td>17</td><td>0.0</td><td>&lt;5</td><td>&lt;5</td></tr><tr><td>Occupation</td><td></td><td></td><td></td><td></td></tr><tr><td>Active working/ employed</td><td>48,186</td><td>67.7</td><td>23,081</td><td>75.6</td></tr><tr><td>Not working</td><td>10,829</td><td>15.2</td><td>2,876</td><td>9.4</td></tr><tr><td>Missing</td><td>12,126</td><td>17.0</td><td>4,561</td><td>14.9</td></tr><tr><td>Education</td><td></td><td></td><td></td><td></td></tr><tr><td>High school</td><td>14,561</td><td>20.5</td><td>5,410</td><td>17.7</td></tr><tr><td>Higher than high school</td><td>38,387</td><td>54.0</td><td>20,668</td><td>67.7</td></tr><tr><td>Lower than high school</td><td>11,232</td><td>15.8</td><td>3,098</td><td>10.2</td></tr><tr><td>Missing</td><td>6,961</td><td>9.8</td><td>1,342</td><td>4.4</td></tr><tr><td>Preconception BMI; mean &amp; SD</td><td>25.9</td><td>5.1</td><td>25.1</td><td>5.1</td></tr><tr><td>Smoking pre-pregnancy (yes)</td><td>3,477</td><td>4.9</td><td>1,070</td><td>3.5</td></tr><tr><td>Missing</td><td>9,320</td><td>13.1</td><td>3,620</td><td>11.9</td></tr><tr><td colspan="5"><strong>Maternal health, other vaccinations, and reproductive history</strong></td></tr><tr><td>Preexisting epilepsy (yes)</td><td>435</td><td>0.6</td><td>193</td><td>0.6</td></tr><tr><td>Pregnancy secondary to IVF (yes)</td><td>2,810</td><td>3.9</td><td>1,453</td><td>4.8</td></tr><tr><td>HPV vaccine within 10 years pre-pregnancy (yes)</td><td>19,456</td><td>27.3</td><td>10,137</td><td>33.2</td></tr><tr><td>Influenza vaccine within 10 years pre-pregnancy (yes)</td><td>18,509</td><td>26.0</td><td>11,029</td><td>36.1</td></tr><tr><td>Influenza vaccine in prior pregnancy (yes)</td><td>6,710</td><td>9.4</td><td>4,320</td><td>14.2</td></tr><tr><td>Risk for severe COVID-19</td><td></td><td></td><td></td><td></td></tr><tr><td>Low</td><td>70,421</td><td>99.0</td><td>30,192</td><td>98.9</td></tr><tr><td>Moderate</td><td>532</td><td>0.7</td><td>250</td><td>0.8</td></tr><tr><td>High</td><td>188</td><td>0.3</td><td>76</td><td>0.2</td></tr><tr><td>Pre-existing asthma (yes)</td><td>4,560</td><td>6.4</td><td>2,338</td><td>7.7</td></tr><tr><td>History of miscarriage or stillbirth (yes)</td><td>17,361</td><td>24.4</td><td>7,328</td><td>24.0</td></tr><tr><td>Missing</td><td>762</td><td>1.1</td><td>138</td><td>0.5</td></tr><tr><td>Prior cesarean section (yes)</td><td>7,153</td><td>10.1</td><td>2,771</td><td>9.1</td></tr><tr><td>Prior pregnancy with major congenital anomaly (yes)</td><td>437</td><td>0.6</td><td>196</td><td>0.6</td></tr><tr><td>Missing</td><td>3,834</td><td>5.4</td><td>1,012</td><td>3.3</td></tr><tr><td>Prior premature delivery (yes)</td><td>1,682</td><td>2.4</td><td>678</td><td>2.2</td></tr><tr><td>Missing</td><td>3,915</td><td>5.5</td><td>1,037</td><td>3.4</td></tr><tr><td>Positive Sars-CoV-2 6 months pre-pregnancy (yes)</td><td>1,810</td><td>2.5</td><td>351</td><td>1.2</td></tr><tr><td colspan="5"><strong>Familial migration status and paternal COVID-19 vaccination</strong></td></tr><tr><td>Maternal primary country of citizenship</td><td></td><td></td><td></td><td></td></tr><tr><td>Norway</td><td>52,618</td><td>74.0</td><td>26,146</td><td>85.7</td></tr><tr><td>Scandinavia</td><td>1,526</td><td>2.1</td><td>742</td><td>2.4</td></tr><tr><td>West/South Europe</td><td>1,158</td><td>1.6</td><td>560</td><td>1.8</td></tr></tbody><tfoot><tr><td colspan="5" style="text-align: right;">(continued on next page)</td></tr></tfoot></table>
<table><caption>**Table 1 (continued)**</caption><thead><tr><th rowspan="2"></th><th colspan="4">Vaccine uptake during pregnancy, any dose</th><th colspan="2">Vaccine uptake during pregnancy, first dose*</th></tr><tr><th colspan="2">No<br>N = 71,141</th><th colspan="2">Yes<br>N = 30,518</th><th colspan="2">Yes<br>N = 17,567</th></tr></thead><tbody><tr><td>Eastern Europe</td><td>6,912</td><td>9.7</td><td>979</td><td>3.2</td><td>608</td><td>3.5</td></tr><tr><td>Middle East</td><td>1,226</td><td>1.7</td><td>183</td><td>0.6</td><td>87</td><td>0.5</td></tr><tr><td>North America and Oceania</td><td>297</td><td>0.4</td><td>155</td><td>0.5</td><td>94</td><td>0.5</td></tr><tr><td>South and Central America</td><td>362</td><td>0.5</td><td>154</td><td>0.5</td><td>316</td><td>1.8</td></tr><tr><td>Africa</td><td>3,264</td><td>4.6</td><td>477</td><td>1.6</td><td>55</td><td>0.3</td></tr><tr><td>East and North-East Asia</td><td>230</td><td>0.3</td><td>96</td><td>0.3</td><td>55</td><td>0.3</td></tr><tr><td>North-Central Asia</td><td>537</td><td>0.8</td><td>82</td><td>0.3</td><td>285</td><td>1.6</td></tr><tr><td>South-East Asia</td><td>1,159</td><td>1.6</td><td>448</td><td>1.5</td><td>305</td><td>1.7</td></tr><tr><td>South and South-West Asia</td><td>1,852</td><td>2.6</td><td>496</td><td>1.6</td><td>119</td><td>0.7</td></tr><tr><td>Maternal migration status</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Born in Norway, both parents from Norway</td><td>43,709</td><td>61.4</td><td>22,985</td><td>75.3</td><td>13,058</td><td>74.3</td></tr><tr><td>Born in Norway or abroad, at least one parent from Norway</td><td>3,785</td><td>5.3</td><td>1,972</td><td>6.5</td><td>1,129</td><td>6.4</td></tr><tr><td>Migrated to Norway</td><td>21,906</td><td>30.8</td><td>5,108</td><td>16.7</td><td>3,139</td><td>17.9</td></tr><tr><td>Born in Norway from migrant parents</td><td>1,739</td><td>2.4</td><td>453</td><td>1.5</td><td>241</td><td>1.4</td></tr><tr><td>Missing</td><td>&lt;5</td><td>—</td><td>—</td><td>—</td><td>—</td><td>—</td></tr><tr><td>Paternal migration status</td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Born in Norway, both parents from Norway</td><td>43,679</td><td>61.4</td><td>22,927</td><td>75.1</td><td>13,047</td><td>74.3</td></tr><tr><td>Born in Norway or abroad, at least one parent from Norway</td><td>3,538</td><td>5.0</td><td>1,828</td><td>6.0</td><td>1,054</td><td>6.0</td></tr><tr><td>Migrated to Norway</td><td>20,082</td><td>28.2</td><td>4,706</td><td>15.4</td><td>2,883</td><td>16.4</td></tr><tr><td>Born in Norway from migrant parents</td><td>1,457</td><td>2.0</td><td>439</td><td>1.4</td><td>238</td><td>1.4</td></tr><tr><td>Missing</td><td>2,385</td><td>3.4</td><td>618</td><td>2.0</td><td>345</td><td>2.0</td></tr><tr><td>Paternal COVID-19 vaccination during pregnancy (yes)</td><td>22,421</td><td>31.5</td><td>27,124</td><td>88.9</td><td>16,612</td><td>94.6</td></tr><tr><td>Paternal age; mean &amp; SD</td><td>33.5</td><td>5.5</td><td>33.7</td><td>5.6</td><td>33.7</td><td>5.7</td></tr></tbody></table>

Abbreviations: SD = Standard deviation; IVF = in-vitro fertility treatment.

education and not working/unemployed status were consistently associated with a decreased likelihood of vaccine uptake in pregnancy, both as any and first dose. Maternal health risk for severe COVID-19, history of prior pregnancies with congenital anomaly or miscarriages were not associated with any dose vaccine uptake in pregnancy. Only history of caesarean section and premature delivery was consistently associated with a negligible lower likelihood of vaccine uptake, using both

definitions. Paternal COVID-19 vaccination during the pregnancy window was strongly associated with greater vaccine uptake in pregnancy, and the magnitude of this association was larger for first dose uptake. As shown in Fig. 2, different familial migration and main citizenship statuses were strongly associated with vaccine uptake in pregnancy, using both definitions. Maternal SARS-CoV-2 infection in the six months pre-pregnancy was consistently associated with a substantial lower likelihood of uptake of any dose (RR: 0.31, 95% CI: 0.26, 0.37) or first dose (RR: 0.32, 95% CI: 0.26, 0.41).

Factors such as smoking before pregnancy, IVF, and uptake of other non-COVID-19 vaccines were not consistently associated with any vaccine dose uptake in terms of direction of the association and/or effect size, before and after the positive national recommendations towards COVID-19 vaccination in pregnancy (Table S7). Fig. S3 shows associations between maternal health, vaccination, and reproductive history factors and vaccine uptake, as ever and first dose, among multiparous pregnancies.

## 4. Discussion

This study reports increasing rates of COVID-19 any dose vaccine uptake in pregnancy, spanning from less than 1 % among deliveries before mid Aug-2021, to 38.8 % in the rest of 2021, and to 48.9 % in 2022. During the overall period, only three out of ten individuals with high risk for severe COVID-19 received at least one COVID-19 vaccine dose while being pregnant, and this estimate decreased to 14 % for first dose uptake. Being at high-risk for severe COVID-19 did not correlate with greater vaccine uptake in pregnancy, but maternal pre-existing asthma did so (9–10 % higher likelihood). We found no evidence that prior miscarriage or pregnancy with congenital anomaly were related to lower vaccine uptake. Only history of caesarean section and premature delivery were negatively associated with COVID-19 vaccine uptake, albeit the effect size of these associations was negligible, especially among multiparous individuals. Paternal COVID-19 vaccination during the pregnancy window emerged as major factor associated with vaccine uptake in pregnancy, and the magnitude of this association was exceptionally large for first dose uptake. Individual maternal factors such as smoking, being unemployed, multiparity, lower education, and younger age were only moderately associated with lower COVID-19 vaccine uptake during pregnancy, whilst the association magnitude was substantial for SARS-CoV-2 infection in the six months pre-pregnancy (68–69 % reduced likelihood). Familial and individual migrant status, and maternal main citizenship from the Middle East, Africa, Eastern Europe, or North-Central Asia, were associated with a considerable decreased likelihood of vaccine uptake while being pregnant.

This study extends prior literature by identifying multiple factors at individual and familial level associated with COVID-19 vaccine uptake during pregnancy and reports novel uptake rates by maternal underlying risk for severe COVID-19 during a two-years period. Our over time

<table><caption>**Table 2**
Uptake of mRNA COVID-19 vaccine during pregnancy by maternal risk for severe COVID-19 or pre-existing asthma.</caption><thead><tr><th rowspan="3"></th><th colspan="4">Risk for severe COVID-19</th></tr><tr><th colspan="2">Low</th><th colspan="2">Moderate</th><th colspan="2">High</th></tr><tr><th>n</th><th>(95 CI)</th><th>n</th><th>(95 CI)</th><th>n</th><th>(95 CI)</th></tr></thead><tbody><tr><td>Any dose vaccine uptake during pregnancy (yes)</td><td>30,192</td><td>30.0 (29.7–30.3)</td><td>250</td><td>32.0 (28.8–35.3)</td><td>76</td><td>28.8 (23.6–34.5)</td></tr><tr><td>First dose vaccine uptake during pregnancy (yes)</td><td>17,410</td><td>19.8 (20.0–20.1)</td><td>127</td><td>19.3 (16.4–22.5)</td><td>30</td><td>13.8 (9.9–19.0)</td></tr><tr><td colspan="7">Pre-existing asthma</td></tr><tr><td></td><th colspan="2">No</th><th colspan="2">Yes</th><th colspan="2"></th></tr><tr><td></td><th colspan="2">n</th><th colspan="2">(95 CI)</th><th colspan="2">(95 CI)</th></tr><tr><td>Any dose vaccine uptake during pregnancy (yes)</td><td colspan="2">28,180</td><td colspan="2">29.7 (29.4–30.0)</td><td colspan="2">2,338</td></tr><tr><td>First dose vaccine uptake during pregnancy (yes)*</td><td colspan="2">16,295</td><td colspan="2">19.7 (19.4–19.9)</td><td colspan="2">1,272</td></tr></tbody></table>

Abbreviations: CI = Confidence Interval.
<figure><img src="image_5.png" /><figcaption>**Fig. 1.** Associations of sociodemographic and life-style characteristics (Panel A for any dose, Panel B for first dose), maternal health, vaccination, and reproductive history (Panel C for any dose, Panel D for first dose) with COVID-19 vaccine uptake in pregnancy. Abbreviations: RR = Risk Ratio; CI = Confidence Interval. All multivariable models are adjusted by calendar time of childbirth, and for clustering by maternal region of residency. The reference categories in Panels A-B include: "high-school education" for educational level, and the counterparts of the other factors (e.g., "married/cohabiting" is reference group for "not married/cohabiting"). In Panels C-D, the reference categories are "no" for all factors (e.g. "No prior premature birth"). Non_COVID-19 vaccinations ever before and history of adverse outcomes are measured within ten years before pregnancy start.</figcaption></figure>

increasing rates of COVID-19 vaccine uptake by pregnant individuals align with prior research including data from Norway up to May 2022, and reflect trust in the national vaccine recommendations [20,39,40]. Any dose COVID-19 vaccine uptake largely coincided with first dose uptake by pregnant individuals in the period between 18-Aug-2021 and end of 2021, which is encouraging. The new emerging knowledge about the favourable reproductive safety of prenatal COVID-19 vaccine exposure may have favoured greater acceptance of COVID-19 vaccination in pregnancy over time [11,41].

The observed low rate of vaccine uptake among pregnant individuals with high risk for severe COVID-19 was consistent for any and first dose vaccine uptake, which is somewhat worrisome. Pregnant individuals with high-risk also had lower likelihood of first dose vaccine uptake than their peers with no/low risk, which is an unexpected result. It is possible that the applied definition for severe COVID-19 risk group [34] may not be fully applicable to childbearing aged individuals as most of high-risk disorders, e.g. organ transplantation and cancer, are rare in this population. Prior research in Norway and Sweden [20] found individuals with pre-pregnancy comorbidities, as broad unique classification, to be more likely to get vaccinated during pregnancy than their peers, albeit the effect size was negligible (8–12 % higher likelihood). The disorders included in our high-risk classification do not fully coincide with those applied by Örtqvist et al. [20], which may explain the discrepant results. Furthermore, we considered pre-existing asthma as a stand-alone disorder, and this disorder was associated with greater vaccine uptake. Prioritizing high-risk individuals for vaccination is crucial due to their increased susceptibility to severe illness, and this also applies to pregnant individuals. In possible future pandemics, vaccination campaigns should better emphasize which specific high-risk disorders are critical for the pregnant and childbearing aged populations.

The substantial association between greater vaccine uptake in

pregnancy and paternal COVID-19 vaccination during the pregnancy window deserves attention. A prior study [24] showed that pregnant individuals who had friend or family member vaccinated against COVID-19 had 84 % reduced odds of reporting vaccine hesitancy than their counterparts, and partner support is critical in the context of pharmacotherapy in pregnancy [27,42]. Paternal migration status was an additional familial factor associated with lower vaccine uptake. Taken together, these data highlight the importance of vaccine educational campaigns for couples, and call for an active involvement of fathers at the phase of clinical counselling, to facilitate the decision-making process regarding benefits and risks of prenatal vaccination.

Although maternal unrealistic risk perceptions of vaccine exposure and fears of adverse effects on the child [26–29,43] were identified as key factors associated with vaccination hesitancy, we found no evidence that prior lived experience of miscarriage or pregnancy with congenital anomaly led to lower vaccine uptake. This result could be attributable to trust towards national authorities and to the provided emerging knowledge about the safety of COVID-19 vaccination for maternal-child health. Only history of prior caesarean section or premature delivery were linked to lower COVID-19 vaccine uptake in our analyses, albeit the effect size was negligible, especially in the analysis restricted to multiparous women. It is possible that vaccine recommendations by policy makers and national authorities did not specifically address possible risk of vaccination in relation to these two outcomes, as they are more subtle than miscarriage or congenital anomaly [44]. Overall, these data suggest that maternal adverse pregnancy history is not strongly related to negative perceptions and attitudes towards vaccination in pregnancy, at least in Norway [43]. Efforts should be made to investigate whether this result also applies to other national and societal context, because this is critical knowledge for providing tailored vaccination counselling to couples who are most hesitant.
<figure><img src="image_6.png" /><figcaption>**Fig. 2.** Associations of familial migration status and paternal COVID-19 vaccination with vaccine uptake during pregnancy as any dose (Panel A) and first dose (Panel B) Abbreviations: RR = Risk Ratio; CI = Confidence Interval. The multivariable model is adjusted by calendar time of childbirth, and for clustering by maternal region of residency. The reference categories are “Norwegian primary citizenship”, “Born in Norway from two Norwegian parents”, and “No Paternal COVID-19 vaccine”. Paternal COVID-19 vaccine was measured during the pregnancy window.</figcaption></figure>

<figure><img src="image_7.png" /></figure>

This study supports prior established associations between lower
COVID-19 vaccine uptake in pregnancy among individuals being
smokers, having lower education and income, younger age, multiparity,
migrant status, and specific citizenships/ethnicities [20,24,45,46]. Our
granular findings by maternal main citizenship support the need of
vaccination campaigns tailored specifically to pregnant individuals from
African countries, the Middle East, Eastern Europe, or North-central
Asia. In line with prior data [24,46], this study shows that uptake of
other vaccines, e.g. against influenza, is proxy of general positive atti-
tude and trust towards vaccination, and this is linked to greater COVID-
19 vaccine uptake rates even by pregnant individuals. Unlike other
studies but also in line with other investigations [27,47], SARS-CoV-2
infection in the six months pre-pregnancy appeared to be a major fac-
tor associated with lower vaccine uptake by pregnant individuals in
Norway. This may be explained by uncertainties regarding durability of
natural immunity [48] coupled to maternal safety concerns about pre-
natal exposure to the COVID-19 vaccine [27].

**5. Strengths and limitations**

The study is based on multiple, nation-wide health registry data in
Norway linked to the MBRN, which covers all deliveries since gesta-
tional week 12. The mandatory registration of COVID-19 vaccination in
the SYSVAK minimizes risk of misclassification of vaccine uptake; since
the SYSVAK records all vaccine doses received independently of preg-
nancy, the study could differentiate between any dose and first vaccine
uptake in pregnant individuals. The comprehensive availability of
clinical diagnoses from primary and secondary healthcare, coupled to
obstetric records from the MBRN, enabled us to adequately classify
maternal risk groups for severe COVID-19 and asthma. Information on
prospective fathers, and the availability of ten years historical data for
mothers, allowed us to explore a vast array of familial and individual
factors associated with vaccine uptake in pregnancy, including granular

details on maternal main citizenship. Lastly, we used multiple imputa-
tion to minimize risk of bias due to missing data [49].

This study also has some limitations that need consideration when
interpreting the results. We used receipt of a vaccine dose as proxy of
vaccine acceptance, which may not fully measure attitude/beliefs to-
ward vaccination. The study could not explore the role of emotional,
social, and religious factors as these are not measured in our national
registries, although these may be important determinants of vaccine
uptake [27]. Political and logistical aspects related to the distribution of
the COVID-19 vaccine in the various counties in Norway was not
measured in the study; to address changes of vaccination recommen-
dation, we repeated the association and descriptive analyses for the
period before and after 18-Aug-2021 [34]. Vaccine doses given abroad
need manual retrospective registration in SYSVAK, leading to uncer-
tainty about how many pregnant individuals received vaccines overseas
without official records in Norway. However, this risk is considered as
minimal, given the necessity of vaccine registration during the study
period. The MBRN does not provide granular information about the type
of occupation in pregnant individuals, and thereby we could not
examine the role of healthcare worker status on vaccine uptake in
pregnancy. Although we examined separately three sets of individual
and familial factors and their standard errors in the final multivariate
models were assessed as satisfactory, we cannot rule out the risk for
multicollinearity or for interaction effects.

**6. Conclusion**

In this registry-linkage study, we observed over time increasing rates
of COVID-19 vaccine uptake during pregnancy, and any dose uptake
largely coincided with first dose uptake in the period between 18-Aug-
2021 through end of 2021. However, COVID-19 vaccination remained
low among pregnant individuals with high risk for severe COVID-19.
Paternal COVID-19 vaccination during the pregnancy window, SARS-
CoV-2 infection pre-pregnancy, individual and familial migration status, and specific maternal main citizenships, emerged as important factors associated with COVID-19 vaccine uptake during pregnancy. We found no evidence that prior miscarriage or pregnancy with congenital anomaly were related to lower vaccine uptake. These findings are useful for the design of targeted intervention and educational vaccination campaigns for couples in possible future pandemics, to facilitate an informed, evidence-based vaccine uptake by pregnant populations.

## Ethics approval

The Regional Committee for Medical and Health Ethics of South/East Norway (no. 285687) approved the study. The Norwegian Data Protection Services for research and the University of Oslo approved the Data Protection Impact Assessment - DPIA (no. 341884).

## CRediT authorship contribution statement

**Jovan Elyass:** Writing – original draft, Formal analysis, Data curation. **Anteneh Desalegn:** Nhung T.H. Trinh: Writing – review & editing, Supervision, Methodology, Data curation, Conceptualization. **Saima Orangzeb:** Writing – review & editing, Validation, Data curation. **Mahmoud Zidan:** Writing – review & editing, Validation, Data curation. **Hedvig Nordeng:** Writing – review & editing, Validation, Methodology. **Angela Lupattelli:** Writing – review & editing, Writing – original draft, Validation, Supervision, Project administration, Methodology, Investigation, Funding acquisition, Formal analysis, Data curation, Conceptualization.

## Declaration of competing interest

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Angela Lupattelli reports financial support was provided by European Union. This work is part of the VERDI project (101045989) which is funded by the European Union. Views and opinions expressed are, however, those of the author(s) only and do not necessarily reflect those of the European Union or the European Health and Digital Executive Agency. Neither the European Union nor the granting authority can be held responsible for them. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

## Data availability

All relevant data are within the paper and its Supporting Information files. No additional data are available.

## Acknowledgments

This work is part of the VERDI project (101045989) which is funded by the European Union. We are grateful to all the participating families in Norway who are part of the health registries and made this research possible.

## Funding

This work is part of the VERDI project (101045989) which is funded by the European Union. Views and opinions expressed are, however, those of the author(s) only and do not necessarily reflect those of the European Union or the European Health and Digital Executive Agency. Neither the European Union nor the granting authority can be held responsible for them.

## Contributions of authors

AL, AD and NTHT conceived the study. AL applied for the study data. AL and JE performed the data analysis, and AD contributed to data curation. AL and JE wrote the initial draft. JE, AD, NTHT, SO, MZ, HN, and AL contributed to data interpretation and to writing the final manuscript. AL obtained funding. The corresponding author attests that all listed authors meet authorship criteria and that no others meeting the criteria have been omitted.

## Appendix A. Supplementary material

Supplementary data to this article can be found online at https://doi.org/10.1016/j.vaccine.2024.126171.

## References

[1] NHS England. NHS encourages pregnant women to get COVID-19 vaccine [Internet]. [cited 2023 Jan 28]. Available from: https://www.england.nhs.uk/2021/10/nhs-encourages-pregnant-women-to-get-covid-19-vaccine/.

[2] Badell ML, Dude CM, Rasmussen SA, Jamieson DJ. Covid-19 vaccination in pregnancy. BMJ 2022;10(378):e069741.

[3] Allotey J, Stallings E, Bonet M, Yap M, Chatterjee S, Kew T, et al. Clinical manifestations, risk factors, and maternal and perinatal outcomes of coronavirus disease 2019 in pregnancy: living systematic review and meta-analysis. BMJ 2020; 1(370):m3320.

[4] Engjom H, van den Akker T, Aabakke A, Ayras O, Bloemenkamp K, Donati S, et al. Severe COVID-19 in pregnancy is almost exclusively limited to unvaccinated women - time for policies to change. Lancet Reg Health Eur 2022;13:100313.

[5] Edlow AG, Castro VM, Shook LL, Kaimal AJ, Perlis RH. Neurodevelopmental outcomes at 1 year in infants of mothers who tested positive for SARS-CoV-2 during pregnancy. JAMA Netw Open 2022;5(6):e2215787.

[6] Fallach N, Segal Y, Agassy J, Perez G, Peretz A, Chodick G, et al. Pregnancy outcomes after SARS-CoV-2 infection by trimester: a large, population-based cohort study. PLoS One 2022;17(7):e0270893.

[7] Conde-Agudelo A, Romero R. SARS-CoV-2 infection during pregnancy and risk of preeclampsia: a systematic review and meta-analysis. Am J Obstet Gynecol 2022; 226(1):68-89.e3.

[8] Santos CAD, Paula AP, Filho GGF, Alves MM, Nery AF, Pontes MGA, et al. Developmental impairment in children exposed during pregnancy to maternal SARS-COV2: a Brazilian cohort study. Int J Infect Dis IJID Off Publ Int Soc Infect Dis 2023. S1201-9712(23)00802-0.

[9] Gurol-Urganci I, Jardine JE, Carroll F, Draycott T, Dunn G, Fremeaux A, et al. Maternal and perinatal outcomes of pregnant women with SARS-CoV-2 infection at the time of birth in England: national cohort study. Am J Obstet Gynecol 2021 Nov; 225(5):522.e1-522.e11.

[10] Edlow AG, Castro VM, Shook LL, Haneuse S, Kaimal AJ, Perlis RH. Sex-specific neurodevelopmental outcomes in offspring of mothers with SARS-CoV-2 in pregnancy: an electronic health records cohort. medRxiv. 2022 Nov 18; 2022.11.18.22282448.

[11] Ciapponi A, Berrueta M, Parker PK, Bardach A, Mazzoni A, Anderson SA, et al. Safety of COVID-19 vaccines during pregnancy: a systematic review and meta-analysis. Vaccine 2023;41(25):3688-700.

[12] American College of Obstetricians and Gynecologists. Statement of strong medical consensus for vaccination of pregnant individuals against COVID-19 [Internet]. [cited 2024 Mar 20]. Available from: https://www.acog.org/news/news-releases/2021/08/statement-of-strong-medical-consensus-for-vaccination-of-pregnant-individuals-against-covid-19.

[13] Skjesol I, Tritter JQ. The Norwegian way: COVID-19 vaccination policy and practice. COVID-19 Pandemic Vaccin Strateg Glob Health Policies 2022;11(2): 100635.

[14] Norwegian Institute of Public Health. Statistics Bank [Internet]. Available from: https://www.fhi.no/en/hn/statistics/statistics-from-niph/statistikkbanker/.

[15] Statistics Norway. Population, by sex, age, contents, year and region [Internet]. Available from: https://www.ssb.no/en/statbank/table/07459/tableViewLayout1/.

[16] CDC Centers for Disease Control and Prevention. COVID-19 Vaccines While Pregnant or Breastfeeding [Internet]. Available from: https://www.cdc.gov/coronavirus/2019-ncov/vaccines/recommendations/pregnancy.html.

[17] Statement of Strong Medical Consensus for Vaccination of Pregnant Individuals against COVID-19 [Internet]. 2021 [cited 2023 Dec 8]. Available from: https://www.acog.org/news/news-releases/2021/08/statement-of-strong-medical-consensus-for-vaccination-of-pregnant-individuals-against-covid-19.

[18] Norwegian Institute of Public Health. Advice and information for women who are pregnant or breastfeeding [Internet]. Available from: https://www.fhi.no/en/op/novel-coronavirus-facts-advice/facts-and-general-advice/advice-and-information-for-pregnant-women/.

[19] Norwegian Institute of Public Health. Pregnancy and breastfeeding [Internet] [cited 2023 Feb 19]. Available from: https://www.fhi.no/en/op/novel-coronavirus-us-facts-advice/facts-and-general-advice/advice-and-information-for-pregnant-women/.
[20] Örtqvist AK, Dahlqwist E, Magnus MC, Ljung R, Jonsson J, Aronsson B, et al. COVID-19 vaccination in pregnant women in Sweden and Norway. Vaccine 2022; 40(33):4686-92.

[21] Citu IM, Citu C, Gorun F, Motoc A, Gorun OM, Burlea B, et al. Determinants of COVID-19 vaccination hesitancy among Romanian pregnant women. Vaccines 2022;10(2):275.

[22] Mustafa ZU, Bashir S, Shahid A, Raees I, Salman M, Merchant HA, et al. COVID-19 vaccine hesitancy among pregnant women attending antenatal clinics in Pakistan: a multicentric, prospective, survey-based study. Viruses 2022;14(11):2344.

[23] Blakeway H, Prasad S, Kalafat E, Heath PT, Ladhani SN, Le Doare K, et al. COVID-19 vaccination during pregnancy: coverage and safety. Am J Obstet Gynecol 2022; 226(2):236.e1-236.e14.

[24] Kiefer MK, Mehl R, Costantine MM, Johnson A, Cohen J, Summerfield TL, et al. Characteristics and perceptions associated with COVID-19 vaccination hesitancy among pregnant and postpartum individuals: a cross-sectional study. BJOG Int J Obstet Gynaecol 2022;129(8):1342-51.

[25] Gibson A, Rand C, Olson-Chen C. Attitudes toward COVID-19 vaccination among pregnant persons in urban hospital-affiliated practices: exploring themes in vaccine hesitancy. Matern Child Health J 2023;27(10):1855-63.

[26] Licata F, Romeo M, Riillo C, Di Gennaro G, Bianco A. Acceptance of recommended vaccinations during pregnancy: a cross-sectional study in Southern Italy. Front Public Health 2023;11:1132751.

[27] Gianfredi V, Berti A, Stefanizzi P, D'Amico M, De Lorenzo V, Moscara L, et al. COVID-19 vaccine knowledge, attitude, acceptance and hesitancy among pregnancy and breastfeeding: systematic review of hospital-based studies. Vaccines 2023;11(11).

[28] Qiu X, Bailey H, Thorne C. Barriers and facilitators associated with vaccine acceptance and uptake among pregnant women in high income countries: a mini-review. Front Immunol 2021;12:626717.

[29] Kilada S, French N, Perkins E, Hungerford D. Pregnant women's attitudes and behaviours towards antenatal vaccination against Influenza and COVID-19 in the Liverpool City Region, United Kingdom: cross-sectional survey. Vaccine X 2023;1 (15):100387.

[30] Irgens LM. The Medical Birth Registry of Norway. Epidemiological research and surveillance throughout 30 years. Acta Obstet Gynecol Scand 2000;79(6):435-9.

[31] Trogstad L, Ung G, Hagerup-Jenssen M, Cappelen I, Haugen IL, Feiring B. The Norwegian immunisation register - SYSVAK. Eurosurveillance 2012;17(16):20147.

[32] Murzakanova G, Räisänen S, Jacobsen AF, Sole KB, Bjarkø L, Laine K. Adverse perinatal outcomes in 665,244 term and post-term deliveries—a Norwegian population-based study. Eur J Obstet Gynecol Reprod Biol 2020;247:212-8.

[33] Bakken IJ, Ariansen AMS, Knudsen GP, Johansen KI, Vollset SE. The Norwegian Patient Registry and the Norwegian Registry for Primary Health Care: research potential of two nationwide health-care registries. Scand J Public Health 2020;48 (1):49-55.

[34] Norwegian Institute of Public Health (NIPH). Coronavirus vaccine – information for the public. Coronavirus vaccine [Internet]. [cited 2023 Aug 14]. Available from: https://www.fhi.no/en/id/corona/coronavirus-immunisation-programme

/coronavirus-vaccine/#about-risk-groups-and-childrenadolescents-with-underlyin g-conditions.

[35] Harel O, Mitchell EM, Perkins NJ, Cole SR, Tchetgen Tchetgen EJ, Sun B, et al. Multiple imputation for incomplete data in epidemiologic studies. Am J Epidemiol. 2018;187(3):576-84.

[36] Carpenter JR, Kenward MG. Multiple imputation and its application. 1st ed. Chichester, West Sussex, UK: Wiley; 2013 [Statistics in practice].

[37] Hosmer DW, Lemeshow S, Surdivant RX. Applied Logistic Regression. 3rd ed. Hoboken: Wiley; 2013 [Wiley Series in Probability and Statistics].

[38] Zou G. A modified Poisson regression approach to prospective studies with binary data. Am J Epidemiol 2004;159(7):702-6.

[39] Siegler AJ, Luisi N, Hall EW, Bradley H, Sanchez T, Lopman BA, et al. Trajectory of COVID-19 vaccine hesitancy over time and association of initial vaccine hesitancy with subsequent vaccination. JAMA Netw Open 2021;4(9):e2126882.

[40] Anderson EC, Blair PS, Finn A, Ingram J, Amirthalingam G, Cabral C. Maternal vaccination provision in NHS maternity trusts across England. Vaccine 2023;41 (49):7359-68.

[41] Buekens P, Berrueta M, Ciapponi A, Bardach A, Mazzoni A, Rodriguez-Cairoli F, et al. Safe in pregnancy: a global living systematic review and meta-analysis of COVID-19 vaccines in pregnancy. Vaccine 2024;42(7):1414-6.

[42] Nasrin T, Tauqueer F, Bjorndal LD, Kittel-Schneider S, Lupattelli A. Partner support for women's antidepressant treatment and its association with depressive symptoms in pregnant women, mothers, and women planning pregnancy. Arch Womens Ment Health 2024;27(4):557-66.

[43] Maisonneuve E, Gerbier E, Tauqueer F, Pomar L, Favre G, Winterfeld U, et al. Determinants of vaccination and willingness to vaccinate against COVID-19 among pregnant and postpartum women during the third wave of the pandemic: a European multinational cross-sectional survey. Viruses 2023;15(5).

[44] Paul KT, Zimmermann BM, Corsico P, Fiske A, Geiger S, Johnson S, et al. Anticipating hopes, fears and expectations towards COVID-19 vaccines: a qualitative interview study in seven European countries. SSM - Qual Res Health 2022;1(2):100035.

[45] Blakeway H, Prasad S, Kalafat E, Heath PT, Ladhani SN, Le Doare K, et al. COVID-19 vaccination during pregnancy: coverage and safety. Am J Obstet Gynecol 2022; 226(2):236.e1-236.e14.

[46] Ha L, Levian C, Greene N, Goldfarb I, Hirsch A, Naqvi M. Association between acceptance of routine pregnancy vaccinations and COVID-19 vaccine uptake in pregnant patients. J Infect 2023;87(6):551-5.

[47] Ramonfaur D, Hinojosa-González DE, Rodríguez RG, Melchor AL, Rodríguez- Ramírez A, Rodríguez-Gómez GP, et al. Determinants of COVID-19 vaccine hesitancy among pregnant persons. J Am Pharm Assoc 2023;63(4):1191-6.

[48] Pooley N, Abdool Karim SS, Combadière B, Ooi EE, Harris RC, El Guerche SC, et al. Durability of vaccine-induced and natural immunity against COVID-19: a narrative review. Infect Dis Ther 2023;12(2):367-87.

[49] Sterne JA, White IR, Carlin JB, Spratt M, Royston P, Kenward MG, et al. Multiple imputation for missing data in epidemiological and clinical research: potential and pitfalls. BMJ 2009;338:b2393.