Patients who experienced an allergic reaction to mRNA COVID-19 vaccines could potentially be eligible to receive the Johnson & Johnson/Janssen COVID-19 vaccine, CDC staff said on a Tuesday call with clinicians.
Currently, patients can be eligible to receive the Johnson & Johnson adenovirus vaccine after receiving one dose of mRNA vaccine only in special circumstances, but the agency is preparing new guidance about this vaccine specifically for individuals with contraindications to the Pfizer/BioNTech or Moderna products.
While agency staff emphasized that the mRNA vaccines are not interchangeable with Johnson & Johnson’s viral vector vaccine, as safety and efficacy of a mixed product series have yet to be evaluated, patients may receive the Johnson & Johnson vaccine in “exceptional” circumstances, such as a contraindication following the first dose of mRNA vaccine.
In these circumstances, an individual may receive the Johnson & Johnson vaccine at least 28 days after the first dose of mRNA vaccine. They are then considered to have received a “valid” Johnson & Johnson “vaccination series.”
However, individuals should not attempt to be vaccinated with both vaccines, nor should they consider getting a dose of Johnson & Johnson vaccine if their second dose of mRNA vaccine is unavailable. And they should not try to get both vaccines for “extra protection.”
“We are recommending if someone has completed a series [with an mRNA vaccine] … they are considered vaccinated, they do not need any additional protection,” said Sarah Mbaeyi, MD, of the CDC. “We are not recommending people substitute in [Johnson & Johnson] if there’s a temporary unavailability of Pfizer or Moderna.”
She referred to current CDC guidance, which states that individuals can wait up to 6 weeks between doses of mRNA vaccine if there is a shortage of second doses.
Mbaeyi also reviewed CDC’s existing clinical considerations for COVID-19 vaccines, including contraindications, such as severe allergic reaction to vaccine ingredients. Current contraindications are the same for all COVID-19 vaccines.
However, she pointed to an important difference between the two vaccine types: while mRNA vaccines contain polyethylene glycol (PEG), Johnson & Johnson’s vaccine contains polysorbate 80. She noted that PEG is the most “important ingredient” in terms of contraindications to the mRNA vaccine.
“No other currently licensed vaccines use PEG, [but] polysorbate is a common ingredient in vaccines across the U.S.,” Mbaeyi said. “PEG and polysorbate are structurally similar” so cross-reactivity is possible, she added.
One important similarity between all three authorized vaccines is all are “non-replicating, not live” vaccines. This means they may be safe for pregnant women, if a clinician determines the benefits outweigh the risks of vaccination.
While there are currently limited data on the safety of Johnson & Johnson’s COVID-19 vaccine in pregnant women, Mbaeyi noted that adenovirus vectors were used for other vaccine development programs, such as the Ebola vaccine, which was studied in pregnant women.
However, she said pregnant women can receive any authorized vaccine, and there is no product preference.
“Based on current knowledge, experts believe COVID-19 vaccines are unlikely to pose risk to a pregnant person or fetus … but, of course, data collection is ongoing,” Mbaeyi said.
When asked about the two-dose regimen that Johnson & Johnson is now testing with its vaccine, Kathleen Dooling, MD, of the CDC, said “duration of protection” could potentially be different than the one dose, though results haven’t come out yet.
CDC’s Advisory Committee on Immunization Practices (ACIP) “will weigh in to see if the benefits suggest two doses would be better than one,” she said.
Dooling was also asked what populations might benefit from the one-dose vaccine, and she suggested people who are going to travel or people who find it difficult to come back for a second vaccine dose.
“Beyond that, this is a vaccine for everybody,” she said.