Vaccination against COVID-19 temporarily changes heart rate variability

Findings of a new systematic review published in the journal MDPI Vaccines describe short-term changes in heart rate variability (HRV), specifically the root mean square of successive differences between normal heart rates (RMSSD) after vaccination against coronavirus disease 2019 (COVID-19). However, short-term changes in HRV parameters normalized within three days after vaccination.

Study: Impact of covid-19 vaccination on heart rate variability: a systematic review. Image credit: totojang1977 / Shutterstock.com

Background

Global vaccination programs were quickly launched to limit the rampant spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the pathogen responsible for COVID-19. However, despite these efforts, vaccination programs face multiple challenges, the most significant of which is vaccination reluctance.

High vaccine resistance rates of up to 25% have raised concerns about the safety of newer and rapidly developed vaccines. Continued research, postmarketing surveillance, increased public awareness, and sharing of evidence-based safety information are recommended to alleviate these concerns.

Vaccination against COVID-19 may lead to temporary neurological symptoms, including dizziness, headache, lethargy, migraine, parosmia and poor sleep quality, according to the World Health Organization (WHO) database of adverse reactions associated with vaccination against COVID-19.

Although rare, there have been some reports of the COVID-19 vaccination causing damage to the autonomic system (ANS). Therefore, HRV is an important and objective metric for assessing the regulation of autonomic balance. In addition, based on HRV data, an association between influenza vaccination and ANS dysfunction was established.

About the study

To help expand evidence-based support for vaccination against COVID-19, the South Korean authors of the current systematic review investigated how vaccination against COVID-19 may affect HRV-related human parameters.

This systematic review included a comprehensive search of four electronic medical databases, including MEDLINE (via PubMed), EMBASE (via Elsevier), PsycARTICLES (via ProQuest), and the Cumulative Index to Nursing and Allied Health Literature (via EBSCO), to examine the potential impact of vaccination against COVID-19 on human HRV. Subsequently, a manual Google Scholar search was conducted on July 29, 2022 to identify missing data that had been reported up to the time of the investigation.

Intervention studies and review articles were excluded from the study. Vaccination against COVID-19 was the only exposure assessed.

Study findings

The studies reviewed suggested that vaccination against COVID-19 led to a short-term reduction in RMSSD values, which could be attributed to self-reported reactions after vaccination. However, asymptomatic participants had mixed results regarding changes in HRV after vaccination.

Other studies have reported that different vaccine types and doses have different effects on HRV parameters. For example, different doses of the Moderna and Pfizer-BioNTech vaccines could be associated with antibody responses to the SARS-CoV-2-receptor binding domain (RBD), while the Johnson & Johnson vaccine was not.

The first dose of the AstraZeneca vaccine, compared to the second dose, led to more significant HRV-related changes.

The second doses of the Moderna and Pfizer vaccines caused more significant changes in HRV than the first doses of these vaccines. Comparatively, the third booster dose of the Pfizer-BioNTech vaccine had a greater impact on HRV stress indicators than the first dose.

In general, vaccinations against COVID-19 had a significantly greater effect on RMSSD in women than in men. In addition, younger patients were more profoundly affected than older individuals.

It should be noted that the methodological quality of the included studies was not optimal. Furthermore, key confounding variables were not measured or adjusted for in the selected studies.

The results of this review confirm that HRV parameters after vaccination against COVID-19 show significant short-term changes that can last up to three days until they finally return to the initial value. Nevertheless, some case reports have been identified describing persistent side effects after vaccination against COVID-19, including postural orthostatic tachycardia syndrome (POTS).

Significant changes in RMSSD, HF and LF/HF ratio were noted in patients with POTS. Therefore, based on the study’s findings, POTS is likely an individualized response to the COVID-19 vaccination rather than a confirmed side effect.

Findings

The study findings provide important insights into the safety of the COVID-19 vaccine from an evidence-based perspective and may have public health implications for reducing vaccine hesitancy. Importantly, this review supports the overall safety of vaccination against COVID-19 in terms of HRV parameters.