No greater risk of hospitalization found after vaccines in MS in study

People with multiple sclerosis (MS) who receive vaccines against influenza — commonly known as flu shots — as well as diphtheria, polio, pneumoccocus, and multiple other pathogens are not significantly more likely to be hospitalized due to a disease relapse, according to a new study in France.

Similar findings were seen between men and women, and across all age ranges, data showed.

The researchers noted that no link was found between the need for hospitalization for an MS flare-up, or relapse, and vaccination, whether “considered overall or individually, regardless of the age group studied.”

“[This] nationwide study of the French population found no association between vaccination and the risk of hospitalization due to MS flare-ups,” the scientists concluded, noting that “immunization by vaccines of the entire population is crucially important for public health.”

The study, “Vaccines and the Risk of Hospitalization for Multiple Sclerosis Flare-Ups,” was published in the journal JAMA Neurology.

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Investigating possible links between MS relapses and vaccines

In MS, the immune system launches an inflammatory attack against healthy cells in the brain and spinal cord. Most patients experience relapses, when old symptoms suddenly return or new ones appear, followed by periods of remission, when symptoms ease or go away entirely.

Mounting evidence suggests that infectious agents, particularly the Epstein-Barr virus, play a role in the development of MS. In general, infectious diseases also have been linked to the risk of MS relapses, or flare-ups.

Vaccines are designed to mimic an infection without causing disease. Each trains the immune system to recognize and fight off that specific infection to prevent or reduce its impact.

However, whether vaccines can trigger MS relapses is unclear, “highlighting the need for well-conducted large-scale studies to examine the association,” the researchers wrote.

To know more, a team of scientists in France examined data from the System of National Health Databases (SNDS) registry, which covers more than 99% of the French population.

A total of 106,523 people with MS were identified, most of whom (71.8%) were women. The mean age of these patients was 43.9 years.

More than two-thirds of the patients (70.3%) had used at least one disease-modifying therapy, and nearly half (47.4%) had received treatment with high-dose corticosteroids — drugs often used to manage symptoms during a relapse.

Seven categories of vaccines were investigated, including DTPPHi — covering the diphtheria, tetanus, poliomyelitis, pertussis, or Haemophilus influenzae vaccines — and those for the hepatitis B virus (HBV), and influenza. Three others were the Pneumococcal vaccine, the Meningococcus vaccine, and the measles, mumps, or rubella vaccines. The last category was for all other vaccines, specifically those for the hepatitis A virus, tuberculosis, varicella virus, and varicella-zoster virus.

For this study, MS relapses were defined as the occurrence of a hospitalization of at least one day with an overnight stay.

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Over half of MS patients given vaccines during 11 years of follow-up

Overall, 35,265 patients (33.1%) experienced a flare-up at least once during the 11 years of follow-up.

In turn, 58,195 individuals (54.6%) received a vaccine at any time during follow-up. The most frequently prescribed vaccines were DTPPHi (30.3%), followed by influenza (19.2%), and pneumococcus (7.0%).

Among patients age 34 or younger, the DTPPHi was the most frequently used vaccine, while the influenza vaccine was the most used in the other age groups. The pneumococcal vaccine was mainly given to those ages 70 or older.

The rates of relapses occurring within 60 days of vaccination were compared with those that happened immediately preceding vaccine administration in each patient.

An analysis revealed no increased risk of MS relapses requiring hospitalization for any vaccine. Similar findings were seen in male versus female patients and across various age groups, including those younger than 18, individuals between 18 and 34 years, those from 35 to 69 years, and individuals older than 70.

No increased risks were observed for the DTPPHi, influenza, and pneumococcal vaccines.

The observable risk pattern remained unchanged when both 30-day and 90-day risk windows were applied. The only exception was the pneumococcal vaccine with a 90-day risk window, which was associated with a 1.6 times increased risk of MS relapses requiring hospitalization.

“No association between overall vaccine exposure and MS flare-ups requiring hospitalization was observed in this large national study,” the researchers concluded.

“Nevertheless,” they noted, “the study cannot completely rule out the existence of a small risk, particularly in the case of the pneumococcal vaccine.”

The team added that, “given the number of vaccine subtypes available, further studies are needed to confirm these results.”