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Advanced Neurology Neurological adverse events post-vaccination

rb for summary totals by vaccine. To minimize the 19 immunizations with symptoms varied by age and
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impact of reporting bias, the normalized frequencies AE (Figure 2 and Table S2). Differences in normalized
of multiple neurological AEs arising within 24 h of frequencies of neurological AEs were observed between
immunization were compared across multiple vaccines; the COVID-19 and influenza (FLU3) vaccines by age group
AEs were normalized to 100,000 VAERS reports for (Figures 2 and 3, Tables S2 and S3). For both influenza and
each vaccine, as shown in Figure 1 and Table S1 for 13 COVID-19, the normalized frequencies increased with age
vaccines. Syncope (loss of consciousness) is a known AE (>60 years old) for AEs: abnormal behavior (>70 years),
that can occur following immunization. For human aphasia (>70 years), cognitive disorder (>80 years),
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papillomavirus quadrivalent (HPV4), the normalized encephalopathy (>80 years), seizure (>80 years), and speech
frequency of syncope is considerably higher than for other disorder (>80 years) (Tables S2 and S3); and for COVID-
vaccines (Figure 1 and Table S1). For the vaccine DTP, the 19 alone, the normalized frequencies increased with age
normalized frequency of seizures is three times that of for delirium (>70 years), and metabolic encephalopathy
DTAP vaccine, and nine times that of influenza (FLU3) (>70 years) (Table S2).
(Table S1). Increased reactogenicity for DTP compared
to DTAP has been previously reported. For abnormal 3.3. Infants (aged 0 – 2) safety signals
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behavior, PNC13 has the highest normalized frequency For infants aged 0, 1, and 2, neurological AEs per
(Table S1). ASD has the highest normalized frequencies 100,000 shots with symptoms are summarized in Table 1
for MMR and Haemophilus B conjugate vaccine (HIBV or for 10 vaccines. The highest number of reports for all
HIB) (Table S1). This is further examined in the following neurological AEs had onset within the first 24 h, followed
section. The normalized frequencies for febrile convulsions in decreasing order by 48 h and 72 h. The Centers for
and syncope are high for meningococcal group B, rDNA Disease Control and Prevention has provided vaccination
absorbed (MENB) vaccine followed by DTP (Figure 1 recommendations based on age. It has been observed that
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and Table S1). For the AE Staring, pneumococcal seizure episodes occurring on the day of vaccination are
(PNC) vaccine is associated with the highest normalized most likely vasovagal syncopal episodes. For infants aged
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frequency (Table S1). 0 – 1, syncope normalized frequencies are higher than for
3.2. COVID-19 and influenza vaccines safety signals those aged 1 – 2 and 2 – 3 (Table 1). Assuming no reporting
bias between identification of syncope and seizure, the
The COVID-19 vaccines were widely administered in the increase in reported seizure AEs associated with the
United States and comprised both the modified mRNA DTP vaccine for infants aged 1 and 2 likely represents a
and adenoviral SARS-CoV-2 spike protein vaccines. The vaccine-specific association (Table 1). In comparison,
frequencies of neurological AEs per 100,000 COVID- the normalized frequencies for abnormal behavior are

relatively low for DTP in comparison to MMR and other
vaccines (Table 1). The normalized frequencies for febrile
convulsions and syncope are high for the MENB vaccine
(Table 1). The normalized frequencies for MMR are also

Figure 1. Day 0 adverse events frequencies per 100,000 vaccinations with Figure 2. Influenza (FLU3) neurological adverse events by age per
symptoms. 100,000 vaccinations with symptoms.

Volume 3 Issue 1 (2024) 4 https://doi.org/10.36922/an.2258