A UK study by University College London has confirmed “small but significant” cases of the serious Guillain-Barre syndrome (GBS), a rare neurological disorder associated with the AstraZeneca vaccine for COVID-19.

The researchers speculate that “the majority or all” of the 121 UK cases of GBS (pdf) in March to April 2021 were associated with first doses of the AstraZeneca vaccine administered in January.

“A similar pattern is not seen with the other vaccines or following a second dose of any vaccine,” said lead author Prof. Michael Lunn on May 30.

The U.S. Food and Drug Administration is limiting the use of Johnson and Johnson's Janssen COVID-19 vaccine as a last resort for adults who cannot accept a shot from another manufacturer.

Though the potential benefits of the vaccine outweigh the risks, the FDA said Thursday that it is restricting the use of the Janssen vaccine. It will be limited to individuals 18 and older and medically ineligible for another approved vaccine and to those who only have access to the J&J vaccine and want one, according to an FDA news release.

U.S. regulators on Thursday strictly limited who can receive Johnson & Johnson’s COVID-19 vaccine due to the ongoing risk of rare but serious blood clots.

The Food and Drug Administration said the shot should only be given to adults who cannot receive a different vaccine or specifically request J&J’s vaccine. U.S. authorities for months have recommended that Americans get Pfizer or Moderna shots instead of J&J’s vaccine.

The Food and Drug Administration (FDA) announced on May 5 that it will restrict the use of the Johnson & Johnson COVID-19 vaccine to adults who can’t receive mRNA vaccines, because of the risk of potentially life-threatening side effects with the J&J shot.

The agency said the COVID-19 vaccine can now only be administered to people aged 18 years of age and older who can’t receive either the Moderna or Pfizer vaccines, both of which are two-dose vaccines and use mRNA technology. J&J’s single-shot vaccine uses adenovirus technology.

A new study found a correlation between an increase in emergency cardiovascular events among people under 40 years of age and the early months of Israel’s COVID-19 vaccine program.

Published in the Nature journal, researchers utilized data from the Israel National Emergency Medical Services between 2019 and 2021 that evaluated emergency, or EMS, calls among 16- to 39-year-olds across Israel “with potential factors including COVID-19 infection and vaccination rates.”

According to Dr. Ryan Cole, messenger RNA (mRNA) vaccines produce persisting spike protein that may cause severe damage to the recipient’s health, such as unusual clotting, heart inflammation, or cancer.

Pfizer and Moderna COVID-19 vaccines are the only mRNA vaccines approved or authorized for booster use in the United States. Johnson & Johnson COVID-19 vaccines use a viral vector, a modified version of a virus, to instruct cells to make antibodies.

Claims that COVID-19 vaccination causes male infertility are still unsupported, experts told Reuters, despite recent social media posts reviving the longstanding allegation.

During the first days of April, some internet users pointed to an article on a website called Study Finds ( here ), entitled: “Male infertility may be a new symptom of long COVID.” Some users commenting on the piece have inaccurately suggested that COVID-19 vaccination – not so-called long COVID - is what causes infertility.

Heart abnormalities were detected in some adolescents months after COVID-19 vaccination, according to a study.

Researchers at Seattle Children’s Hospital reviewed cases of patients younger than 18 who went to the hospital with chest pain and elevated serum troponin levels, two key markers of heart inflammation, within a week of getting a second dose of Pfizer’s COVID-19 vaccine.

Social media users are falsely claiming that a Swedish study conducted by Lund University found that mRNA COVID-19 vaccines permanently alter human DNA.

The text in one post reads: “BOMBSHELL: Biological Study PROVES Pfizer mRNA Vaccine Permanently Alters Human DNA”.

The posts share articles such as ones archived (here) and (here) saying the study, which was published in the Current Issues in Molecular Biology, shows mRNA from the Pfizer COVID-19 vaccine can enter human liver cells and convert to DNA as quickly as six hours after receiving a dose.

Following the publication of an  article from National Public Radio about an increase in stroke rates among young people, anti-vaccine figures on social media were quick to raise speculation about the coronavirus vaccine’s role in the increase.