Vials containing the Janssen Coronavirus Disease (COVID-19) vaccine from Johnson & Johnson.

Johnson & Johnson via Reuters

100 cases of a rare but serious neurological disorder have been reported following Johnson & Johnson Covid-19 vaccinations, but preliminary data suggests the benefits of vaccinations still outweigh the risks, the Centers for Disease Control and Prevention said on Thursday with.

According to slides released the Thursday before a presentation to the CDCs, there were 8.1 cases of Guillain-Barre syndrome per 1 million doses, which is higher than expected in the general population and almost eight times what was seen in the recordings of Pfizer and Moderna Advisory Committee on Vaccination Practices. Guillain-Barre is a rare neurological disorder in which the body’s immune system mistakenly attacks part of the nervous system.

The data does not show a similar pattern with the Pfizer or Moderna vaccines, the US agency said. By comparison, there was about one case of Guillain-Barre per million doses in people who received one of the two-dose mRNA vaccines, according to the agency.

The additional data comes a little over a week after the Food and Drug Administration announced a new warning for J&J inclusion after preliminary reports of Guillain-Barre syndrome were found in some J&J recipients.

The new warning was just the latest setback for J&J, who suffered production problems with their vaccine as well as public concerns about a rare, potentially life-threatening blood clotting disorder associated with their vaccines.

J&J is researching early on whether potential modifications to its Covid vaccine could reduce or eliminate the risk of vaccine-induced immunothrombotic thrombocytopenia (VITT) in some recipients.

Rare side effects that scientists say are common have also been seen with the Pfizer and Moderna vaccines.

In late June, the FDA added a warning to patient and vendor datasheets for the mRNA vaccines to indicate a rare risk of heart inflammation. Both vaccines now contain a warning of myocarditis and pericarditis after the second dose. Myocarditis is the inflammation of the heart muscle and pericarditis is the inflammation of the tissues surrounding the heart. Health officials said the benefits of vaccination still outweigh the risk.

Of the 100 reported cases of Guillain-Barre syndrome, 95 people were seriously ill, according to the CDC. One person – a 57-year-old man with previous illnesses – died. According to the information, most of the reported cases occurred around two weeks after vaccination and mostly in men with an average age of 57 years. More than 12 million of the J&J shots were administered in the United States, according to the CDC.

– CNBC’s Rich Mendez and Robert Towey contributed to this article.