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TITLE OF THE ARTICLE
:
POST-VACCINATION IMMUNITY TO MEASLES IN
CHILDREN WITH POST-COVID SYNDROME
Kenzhayeva Dilorom Toshtemirovna
Assistant at the Department of "Propaedeutics of Childhood Diseases, Pediatrics, and
General Practice"
Akhmadova Durdona Kamol kizi
4th-year student, Faculty of General Medicine, Termez Branch of the Tashkent Medical
Academy
Abstract:
This article examines the impact of post-COVID syndrome on post-vaccination
immunity to the measles virus in children. A total of 89 children undergoing outpatient and
inpatient treatment were examined between 2024 and 2025. Post-COVID syndrome was
diagnosed by ELISA testing for IgG antibodies to SARS-CoV-2, and immunity to measles
was assessed using the VectoMeasles-IgG ELISA test. A decrease in measles-specific
antidiv titers was found in previously vaccinated children with post-COVID syndrome.
The study highlights the importance of monitoring and revaccination in cases of
seronegative results.
Keywords:
measles, vaccination, post-vaccination immunity, post-COVID syndrome, IgG
antibodies, SARS-CoV-2, ELISA, children, revaccination, immune status, VectoMeasles,
epidemiology, seronegativity, post-COVID immunity, prevention
Introduction
Measles remains one of the most contagious vaccine-preventable infections, despite
widespread implementation of routine immunization. Since the COVID-19 pandemic,
special attention has been given to the effects of coronavirus infection and post-COVID
syndrome on immune system function, especially in children.
The relevance of this research lies in clinical and laboratory findings indicating a decline in
previously developed post-vaccination immunity in children who have recovered from
COVID-19. This may lead to renewed outbreaks of measles among vaccinated pediatric
populations.
Post-COVID syndrome (also known as Long COVID) refers to a range of symptoms that
persist or emerge at least four weeks after the acute phase of COVID-19, regardless of the
initial severity. The World Health Organization (WHO) defines post-COVID syndrome as a
condition occurring in individuals with confirmed or probable SARS-CoV-2 infection, in
which symptoms last for at least two months and cannot be explained by alternative
diagnoses.
Although the pathophysiological mechanisms of post-COVID syndrome are not fully
understood, possible factors include chronic inflammation and immune dysregulation,
autoimmune reactions triggered by molecular mimicry, viral RNA persistence,
microvascular damage with hypercoagulability, autonomic nervous system dysfunction, and
psycho-emotional consequences of the disease.
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This syndrome poses particular risks for children, including multisystem inflammatory
syndrome in children (MIS-C) and subtle disruptions in immune homeostasis. Symptoms
commonly include chronic fatigue, shortness of breath, "brain fog," headaches, palpitations,
muscle and joint pain, sleep disturbances, anxiety, depression, rashes, and low-grade fever.
In children, additional signs may include emotional instability, reduced academic
performance, gastrointestinal issues, and weakened immune responses, including reduced
antidiv titers from past infections or vaccinations.
Diagnosis of post-COVID syndrome requires a comprehensive approach, including clinical
observation, validated questionnaires, laboratory tests (especially IgG ELISA for SARS-
CoV-2), functional testing (e.g., pulse oximetry, ECG, pulmonary function tests), and ruling
out other chronic or acute conditions.
In this study, post-COVID syndrome in children was confirmed by ELISA testing for IgG
antibodies to SARS-CoV-2, with titers above 1 IU/mL considered significant. To investigate
the effect of post-COVID syndrome on measles post-vaccination immunity in children and
evaluate the need for revaccination.
Between 2024 and 2025, 89 children were examined, both as outpatients and inpatients. All
had previously received measles vaccinations in accordance with the national immunization
schedule. To confirm past SARS-CoV-2 infection and diagnose post-COVID syndrome,
ELISA was used to detect IgG antibodies. Post-COVID syndrome was diagnosed when IgG
levels exceeded 1 IU/mL.
To evaluate measles-specific post-vaccination immunity, the VectoMeasles-IgG ELISA test
(Novosibirsk) was employed for quantitative detection in serum. Thresholds were
interpreted as follows: <0.12 IU/mL — seronegative (no immunity) 0.13–0.17 IU/mL —
weakly positive (low immunity) 0.18 IU/mL — positive (adequate immunity)
Results showed that a significant proportion of children with post-COVID syndrome had
reduced antidiv levels against measles, despite full vaccination. Among them, 32% were
seronegative (<0.12 IU/mL), indicating a complete absence of measles-specific immunity.
Additionally, 21% had low-positive results requiring follow-up.
These findings suggest that COVID-19, through immune system disruption, may impair or
eliminate previously established immunity. Such changes are especially concerning given
declining vaccination coverage and rising vaccine hesitancy. Therefore, post-COVID
syndrome in children should be considered a risk factor for reduced resistance to measles,
even in vaccinated individuals.
Conclusion
This study confirmed a decrease in post-vaccination immunity to measles in children with
post-COVID syndrome. The significance of the issue lies in the potential increase in measles
cases among vaccinated children. Early diagnosis of immune status allows timely
identification of at-risk groups and prevention of disease spread. Effective treatment of post-
COVID syndrome is enhanced through a comprehensive approach including immunological
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monitoring. Measles prevention in this population requires special attention, including
revaccination when antidiv titers fall below 0.12 IU/mL.
References
1.
Baranov A.A., Aleynikova E.N. Post-COVID Syndrome in Children and
Adolescents. — Pediatrics, 2022, No. 3, pp. 25–31.
2.
Brylyakova E.A., Frolov A.F. Measles: Current Situation and Prevention. —
Infectious Diseases, 2021, No. 2, pp. 14–19.
3.
Temporary Guidelines of the Ministry of Health of the Russian Federation. “Features
of COVID-19 in Children”, 2023.
4.
State Research Center for Virology and Biotechnology “Vector”. User Manual for
VectoMeasles-IgG ELISA Test. — Novosibirsk, 2024.
5.
World Health Organization. Measles vaccines: WHO position paper – April 2023.
Weekly Epidemiological Record, 2023; 98(14): 129–144.
6.
Litvinova E.A. Post-Vaccination Immunity: Challenges and Solutions. — Journal
“Immunology”, 2022, No. 1, pp. 5–11.
7.
Akhmedova S.Sh., Rakhimova F.T. Diagnosis and Prevention of Measles in the
Post-Pandemic Period. — Tashkent, 2023, pp. 42–47.
