Children with JIA with remission without treatment or on the long-term treatment conventional or even biological disease-modifying antirheumatic drugs (DMARDs), may be safely vaccinated for COVID-19.

COVID-19 vaccination does not interfere with the JIA treatment and does not exacerbate the rheumatoid process.

Vaccination is the most effective strategy to prevent and reduce the effects of the coronavirus disease 2019 (COVID-19) pandemic. Both randomized studies and further observations proved COVID-19 vaccines efficacy in reducing SARS-CoV-2 infection rates and severity of disease (1). However, patients with an immune dysfunction related either to the rheumatic disease or the use of immune-modulating drugs, could have altered COVID-19 vaccination response. Therefore, the answer to the question whether vaccination of a child with rheumatic disease is effective and safe is very important.

Juvenile idiopathic arthritis (JIA) is the most common rheumatic disease in childhood and includes various forms of arthritis, which begin before the age of 16 years, persist for more than 6 weeks and do not have determined cause. Therapeutic process involves treatment with disease-modifying antirheumatic drugs (DMARDs), including conventional (cDMARDs) and biological (bDMARDs) agents. In some cases, administration of short-term non-steroidal anti-inflammatory drugs and systemic or intraarticular glucocorticosteroids may be necessary (2).

Although adult and pediatric patients with rheumatic diseases treated with DMARDs do not seem to present a greater risk of COVID-19 or a worse disease outcome compared to the general population (3–5), some reports indicate a possible more severe course of the disease (6, 7).

The course of SARS-CoV-2 infection in patients with JIA is similar to the course of COVID-19 in the general pediatric population, despite JIA patients receiving immunosuppressive therapy. However, observations indicate that SARS-COV-2 infection may cause exacerbation of the disease, which required escalation of therapy (3, 7).

Vaccination of children with rheumatic disease is still important issue for rheumatologists and paediatricians. The Paediatric Rheumatology European Society (PRES), scientific society for healthcare professionals in paediatric rheumatology, has issued recommendations on vaccination for children with rheumatic diseases (8, 9). Despite the recommendation many children with JIA do not receive the COVID-19 vaccination due to fear of vaccine adverse events. In our experience parents and patients, as well as, health professionals are concerned about the exacerbation of the underlying disease and the unknown effects of the new vaccine. Faced with many questions and concerns from parents, patients, as well as, doctors about COVID-19 vaccination in children with rheumatic diseases, the aim of our study was an assessment of the COVID-19 vaccine safety and effectiveness in children and adolescents with JIA. The main objective of the study was to evaluate the incidence of adverse events after COVID-19 vaccine in patients with JIA and the impact of vaccination on disease activity.

Collected data were analysed with STATISTICA software (Poland). For continuous variables, their distributions were assessed using Shapiro-Wilk test. Due to most continuous characteristics having a non-normal distribution (CRP, ESR) or being measured on an ordinal scale, we proceeded with non-parametric approach. For paired observation, Wilcoxon test was applied and results were reported as before/after medians with 25%–75% ranges and median differences (with 25-75% range). In case of heavily 0-centred distributions where median values were uninformative, the variables were categorized and numbers and percentages were provided additionally.

Categorical data were assessed and presented as numbers and percentages. For paired comparison, McNemmar's test was used. Unpaired comparisons such as frequencies of adverse effects between different treatment regimens were performed using Chi² test.

In all analyses, alfa for declaring statistical significance was chosen as 0.05.

Our study demonstrated a good vaccine safety profile in JIA patients. None of the patients experienced an allergic reaction or other form of serious adverse events following COVID-19 vaccination. After the first dose of COVID-19 vaccine more than a half study group presented mild adverse events: arm pain or oedema at the application side, one patient reported additionally weakness. Also more than half of the children (58.14%) had adverse events after second dose of COVID-19 vaccine, however the spectrum of the symptoms was wider. Most of these were local reactions (arm pain or oedema at the application side) and mild to moderate systemic adverse events: weakness, headache, fever, in one patient lymphadenopathy and in one—arrythmia. Myocarditis and pericarditis have rarely been reported and when reported, the cases have especially been in adolescents and young adult males within several days after mRNA COVID-19 vaccination (Pfizer-BioNTech or Moderna)—usually within a week of vaccination and more often after the second dose (12). All symptoms completely resolved. The incidence of adverse events following COVID-19 vaccination was not dependent on the treatment used in patients.

Our observation did not show a negative effect of COVID-19 vaccination on disease activity. We even saw a slight improvement comparing to the pre-vaccination assessment, that was probably connected with longer period of JIA treatment, however indicated that vaccination did not exacerbate disease course. During the 3-month follow-up period after vaccination, none of the patients developed SARS-CoV-2 infection.

We are aware that not all children with rheumatic diseases have been vaccinated despite the recommendation. Nevertheless, we would like to point out that all parents and all eligible siblings of included patients with JIA had been vaccinated against COVID-19. None of them experienced an allergic reaction or a serious adverse events following COVID-19 vaccination.

In May 2021, the first COVID-19 vaccine (Pfizer-BioNTech), was approved by the European Medicines Agency (EMA) for children aged 12 years and older, followed by another vaccine, (Moderna vaccine), in July 2021. In November 30, 2021 EMA approved Pfizer-BioNTech vaccine for use also in children 5 years of age and older in Europe (13, 14).

In Poland, vaccination against COVID-19 for adults and adolescents over 16 years of age began on December 27, 2020, as in other European Union countries. According to the Republic of Poland website gov.pl (15), more than 54 million vaccines were administered until 4 July 2022. Currently, 22,516,851 people are fully vaccinated, representing 59.9% of total Polish population. On June 7, 2021, the 1st COVID-19 vaccine for children aged 12–15 years was approved in Poland, and on December 12, 2021 also for children from the age of 5. On January 22, 2022, a booster dose was approved for adolescents 12–15 years of age. By July 4, 2022, approximately 3,3 million doses were administered in the 5–17 age group. According to Statistics Poland (16), the population aged 0–17 is 6.9 million, which means that many children and adolescents remain unvaccinated.

Both, PReS and Polish Society of Rheumatology recommended vaccinations for children with rheumatic diseases (17).

There are few reports on the safety and efficacy of vaccination against COVID-19 in children and adolescents with rheumatic diseases. Physician and guardians are concerned about the safety of patients, both in terms of adverse events and the impact on the activity of the disease.

Haslak, et al. indicated in similar like our study an acceptable safety profile of mRNA COVID-19 vaccines in children with inflammatory rheumatic diseases. They monitored 246 patients (receiving biological or other therapies) aged 12—20.1 years. The most common adverse events were fatigue (27.6%), headache (17.9%), myalgia (15.4%), arthralgia (15.4%) and fever (14.2%). Only 3 subjects (2 patients with familial mediterranean fever, and one healthy child) were considered to have experienced serious adverse events requiring hospitalization. Local reactions were seen in 8.1%, and 12.1% children had disease flares within 1 month after the vaccines. There was no significant relationship between adverse events frequency and age, gender, activity of the diseases and treatment (18).

Dimopoulou, et al. evaluated the immunogenicity of the COVID-19 vaccine in 21 adolescents with JIA aged 16–21years on TNF-inhibitors treatment (15—together with methotrexate). All patients developed a sustained humoral response against SARS-CoV-2 assessed 1 and 3 months after vaccination. None of the participants developed disease flare during the 3 months follow-up period (19) similar to our observations. Local reactions were more frequent (74%) that in ours group, but systemic reactions were relatively infrequent (19%). As in our study, the most of localized and systemic reactions were noted after the second dose of the vaccine. Also, no exacerbation of underlying disease was noted, based on evaluation of the JADAS-27 scale at 1 month before the vaccination, as well as at 1 and 3 months after the second dose (20).

Heshin-Bekenstein, et al. presented their observations on the safety and immunogenicity of the anti-SARS-CoV-2 vaccine in 91 patients: adolescents (ages 12–18 years) and young adults ages 18–21 years) with juvenile-onset inflammatory rheumatic diseases, including 42 with JIA, and 80% of those patients were receiving immunomodulating drugs. Authors reported good safety profile: 96.7% of patients reported mild or no side-effects, and no change in disease activity. However, 3 patients had transient acute symptoms: renal failure and pulmonary haemorrhage following the first vaccination and mild lupus flare and viral infection following the second dose. Likewise in our study no cases of COVID-19 were documented during the 3-month follow-up (21).

Also, the observations of Arslanoglu, et al. demonstrated a good safety profile of the COVID-19 vaccine in 228 children with rheumatic diseases (99 patients with JIA), regardless the treatment (conventional or biological). Adverse events after the first dose of vaccine were recorded in 93 (54.7%) patients and in 66 (52.4%)—after the second dose. No serious adverse events including myocarditis, anaphylactic shock, or death were observed (22). This study also confirmed our observations that vaccines should not cause flares of rheumatic diseases in children and adolescents.

There are some limitations of the study. There was no control group of healthy children included into the study. Moreover, the observational period was short—maximum 3-month follow-up. Part of the children got only one dose of vaccine, mainly those who were younger than 12 years old, as the COVID-19 vaccine for the children 5–11 years was available later than for those over 12 years. It would be valuable to provide data of serological profile of patients, in order to demonstrate the efficacy of vaccine, however it was the questionnaire study.

Summing up, our study and all the studies published so far confirm the safety of COVID-19 vaccine in pediatric population. Our group of patients covers children with different age than previously published. Nevertheless, although the published studies differ in the age of the observed patients, the type of diagnoses and applied therapies, all of them, together with ours, indicate the safety of COVID-19 vaccines in children and adolescents with rheumatic diseases. We are aware that not all of patients have been vaccinated despite the recommendation due to still concerns among parents about COVID-19 vaccine safety. We hope our study will help alleviate the doubts of patients, parents and some healthcare professionals about this important vaccination. Especially that we have reasons to be afraid of the next wave of the SARS-CoV-2 infections.

Our study found that children and adolescents with JIA with remission without treatment or on the long-term treatment—cDMARDs or even bDMARDs, can be safely vaccinated for COVID-19. Moreover, we found no evidence that COVID-19 vaccination does interfere with the JIA treatment and can exacerbate symptoms of the disease. Vaccination protected against developing COVID-19 during follow-up.

The presented analysis of our local Polish experience may become helpful in everyday practice of pediatric rheumatologist who may refer to the findings of this study during conversation with patients or parents regarding the efficacy and safety of COVID-19 vaccines. Our observations are also important for future vaccination recommendations in JIA patients.