This study provided important data about the impact of COVID-19 vaccine on seizures in PWE. Our results indicated that seizure (within 14 days after vaccination) was a frequent side reaction (13.8%) in PWE after vaccination. The binary logistic regression analysis revealed that seizures within three months before vaccination and withdrawal or reduction of ASM during the peri-vaccination period were correlative factors. In addition, vaccination may be safer for patients with normal EEG results. As far as we know, no studies have been conducted to evaluate the risk of seizures in PWE after COVID-19 vaccination. As the first study to assess the risk of seizures after COVID-19 vaccination, our findings provide critical guidance to PWE regarding vaccination.
This study chose seizures within 14 days after vaccination as the primary observation index rather than seizure frequency. This was because PWE with frequent seizures were not allowed to be vaccinated against COVID-19 in China. Therefore, for PWE with infrequent seizures, no appropriate comparison target for seizure frequency existed. Although taking perampanel or lacosamide was statistically significant in univariate analysis, we excluded them from the binary logistic regression analysis. This was because we believed that demographic characteristics of patients who took these two drugs were significantly different from those taking other ASM. We analyzed the distribution of seizure-free duration grades in patients treated with these two drugs and found statistically significant differences. These two medications were only recently approved in China, and few patients used them for more than two years, let alone seizure-free for more than two years (in fact, none of patients taking perampanel or lacosamide in our study was seizure-free for more than two years).
At present, a large-scale injection of COVID-19 vaccine in China has just started, and many people, including PWE, are skeptical about the vaccine's safety. Our results revealed that the safety of COVID-19 vaccine was worthy of recognition. Among 290 patients, 62 (21.4%) experienced mild non-epileptic side reactions, while only 2 (0.7%) had serious side reactions. However, for the special population of PWE, whether to vaccinate against COVID-19 still needs to be considered. In our study, 13.8% of PWE experienced seizures within 14 days after vaccination, which is much higher than previous studies of other vaccines; by contrast, even in patients with Dravet syndrome, the rate of seizures after MMR vaccination was only 2.3%.15 Karina et al. found that the risk of seizures following vaccination with various vaccines did not even increase.16 In our study, the high seizure rate after COVID-19 vaccination may be due to the following reasons: 1. first, most patients in the SAV group have a seizure-free duration of less than three months. For these patients whose epilepsy control status was not ideal, the seizures after vaccination may be derived from the characteristics of epilepsy itself, but not vaccination. 2. Verbeek et al. found that the longer the use of ASM, the higher the risk of post-vaccination seizures in children with epilepsy.15 In our study, the minimum age of patients was 14, implying that our patients used ASM for a longer time than childhood epilepsy patients; demographic characteristics may lead to such results. 3. Mental disorders can promote the onset of epilepsy.17 Unlike vaccines such as DTP and MMR, COVID-19 vaccination has not started too long. PWE continues to have concerns about the vaccine's safety and effectiveness, resulting in mental health problems in PWE following vaccination and then increasing seizures.
Unsurprisingly, injecting COVID-19 vaccine can induce seizures. Aladdin et al. once reported a case of refractory status epilepticus after ChAdOx1 nCoV-19 vaccine injection.18 Although DTP and MMR can promote seizures by inducing additional fever,3,13 in our study, the three patients who developed a fever after vaccination did not experience seizures. Therefore, the mechanism by which COVID-19 vaccine promotes seizures may not be correlated with fever induction. Existing studies have proved that coronaviruses, particularly β-coronavirus to which SARS-CoV-2 belongs, were not limited to infecting the respiratory tract but often invaded the central nervous system (CNS).19 SARS-CoV-2 virus can enter CNS through a variety of ways: spreads through blood and crosses blood-brain barrier (BBB); spreads across synapses; and enters through blood-cerebrospinal fluid or structures around ventricles.[20] After entering CNS, the virus mainly binds to various nerve cells through angiotensin-converting enzyme 2 (ACE2).20 Coronavirus mainly infected neurons in the brainstem associated with cardiopulmonary control; damage to these areas may aggravate respiratory depression and even lead to respiratory failure,19 and can also increase the risk of sudden epileptic death.21 In addition, SARS-CoV-2 infection can induce a systemic inflammatory storm and release many pro-inflammatory factors, resulting in BBB destruction, damage of glia limitans, activation of Toll-like receptors in microglia, and astrocytes, and ultimately promoted neuroinflammation, which may severely disrupt brain homeostasis and cause neuronal death.22,23 On the one hand, many studies have revealed that activating Toll-like receptors can cause epilepsy;24,25 On the other hand, BBB disruption can cause entry of immune cells and serum proteins from peripheral blood into the brain, promoting the occurrence of epilepsy.25,26 Finally, SARS-CoV-2 transcriptome had molecular similarities with the epitopes of human CNS protein, producing various autoantibodies and may eventually trigger autoimmunity to aggravate inflammatory storms.20 Overall, we imply that SARS-CoV-2 induces epilepsy mainly through an inflammatory cascade. Given the potential epileptogenic capacity of SARS-CoV-2, we do not propose injecting attenuated vaccines in PWE.
In the binary logistic regression analysis, seizures within three months before vaccination were a correlative factor with statistical significance. The results revealed that, in the three months before vaccination, the risk of seizures in patients with seizures was 10.121 times that of those who were seizure-free (P<0.001, 95% CI: 4.301-23.816). Therefore, PWE who are seizure-free for at least three months can be considered for vaccination. In China, "uncontrolled epilepsy" was a contraindication to COVID-19 vaccination, but no accurate definition for "uncontrolled epilepsy" existed. A study defined it as having a seizure within 12 months.27 However, in univariate analysis, we found that for patients with a seizure-free duration of more than three months, as duration was further extended, the seizure rate after vaccination would not change significantly. Therefore, we considered "uncontrolled epilepsy" as having any seizure within three months. However, it should be noted that 7.8% of patients who were seizure-free for more than three months experienced seizures after vaccination. Another correlative factor with statistical significance was withdrawal of reduction of ASM during peri-vaccination period (P=0.027, OR=4.452, 95% CI: 1.182-16.768). According to this, we suggest that ASM reduction should be forbidden during peri-vaccination period. For patients with well-controlled seizures who have withdrawn, whether they need to retake ASM should be based on EEG results. Finally, regardless of EEG results, patients who withdraw by themselves must retake ASM.
Our study included a factor that was not statistically significant but worthy of attention. Although EEG results of 69 patients were not significantly different between the two groups, 32 of 33 patients (97.0%) who had no seizures within three months before vaccination and had normal EEG results did not experience any seizure following vaccination. According to a meta-analysis by Lamberink et al., abnormal EEG before drug withdrawal was a risk factor for epilepsy recurrence in PWE after drug withdrawal.28 This means that compared with PWE who have abnormal EEG, PWE with normal EEG have a better seizure control status and are therefore less likely to develop seizures induced by various factors. Therefore, for PWE who are seizure-free for at least three months and whose EEG results are normal before vaccination, it will be safer to vaccinate against COVID-19.
Additionally, our study had some limitations. First, this was a retrospective study, with small sample size and lack of control. Second, the patients’ seizure information was mainly obtained from patients themselves or their relatives, ignoring seizures in some PWE. Third, we only divided seizure-free duration into five levels, and too large intervals may affect the accuracy of our results. Finally, because patients were received inactivated vaccinations, our conclusions may not be generalizable to other types of vaccines. In the future, prospective randomized controlled studies with a large sample may be required to further evaluate the impact of COVID-19 vaccination on seizures in PWE.