Health personnel first to receive booster doses 3:16
(CNN) -
Calls and emails about booster doses of COVID-19 vaccines have already started pouring in at Dr. William Schaffner's office in Nashville, Tennessee.
It all started last week, when the US Food and Drug Administration and the US Centers for Disease Control and Prevention (FDA and CDC, respectively) recommended an additional dose for certain immunosuppressed people who they had received the COVID-19 vaccines from Moderna or Pfizer / BioNTech.
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Then on Monday, officials in the Biden administration said they are working on a plan to recommend more Americans receive a booster dose about eight months after being fully vaccinated with the Pfizer or Moderna vaccines.
The issue will be addressed during a covid-19 briefing at the White House on Wednesday.
But nearly 14 million fully vaccinated people in the United States did not receive one of those mRNA vaccines.
They received the Johnson & Johnson single-dose vaccine and, so far, are not part of this booster dose conversation.
"Our J&J patients have not been overlooked or neglected. It's just the way the data comes in," said Schaffner, a professor in the Division of Infectious Diseases at Vanderbilt University Medical Center.
To J&J vaccine patients who are calling and emailing about boosters, he tells them to wait.
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"You can't make good recommendations without the data," he said.
Last month, J&J researchers reported that the vaccine provides immunity that lasts at least eight months and possibly longer.
Study evaluates whether booster dose of J&J is necessary 0:45
The J&J vaccine also appears to provide adequate protection against the delta variant, the predominant strain of the virus currently sickening in the United States.
J&J said in July that a second dose or booster dose of its vaccine would not be necessary at that time.
However, a Johnson & Johnson spokesperson told CNN on Tuesday that the company is gathering additional data to see if booster shots are necessary.
"Ensuring durable and long-term protection against hospitalization and death is critical to curbing the covid-19 pandemic," the company said in an email to CNN.
"Johnson & Johnson continues to diligently generate and evaluate evidence from ongoing trials, as well as emerging real-world evidence, while assessing the need for a Johnson & Johnson COVID-19 vaccine booster."
Different vaccines, different studies, different timelines
Many vaccines need more than one dose to provide complete protection.
Some, like tetanus, need an extra boost every 10 years or so because immunity wanes over time.
Others, like the flu, must be given annually because each flu season brings new strains.
In the case of covid-19, scientists are still finding out how long the protection lasts and how vaccines work against the different variants.
All of this will need to be determined through further research.
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Regarding mRNA vaccines, more data is being obtained.
Pfizer said Monday that it has submitted initial data supporting the use of boosters to the FDA.
Moderna said last week that it is still in the process of submitting its data.
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Johnson & Johnson's vaccine works somewhat differently from mRNA vaccines, which use newer technology that delivers genetic material directly to cells through fat particles.
The J&J vaccine uses a viral vector, a genetically engineered common cold virus to infect cells, but does not replicate or spread in the body.
The vector sends genetic instructions to cells and trains them to identify and protect against the coronavirus.
Johnson & Johnson has also always been on a different timeline.
When Pfizer / BioNTech and Moderna received authorization in December, J&J was still collecting data.
It got its emergency use authorization a couple of months later, in February.
And while there is evidence that immunosuppressed people may benefit from a third dose of an mRNA vaccine, it is not yet clear whether immunosuppressed people who received the J&J vaccine would benefit from receiving another dose.
"We have been reviewing the science and data almost daily to assess whether or when boosters are needed," the CDC said in an email to CNN when asked about boosters for the general public and for the immunosuppressed on Tuesday.
"As we have said, reinforcements are likely to be needed. More detailed plans will be announced soon, so we will have more information then. All of this will be done in accordance with independent review and recommendations from the FDA and CDC."
Mix and match vaccines
It is also unclear whether people who received the J&J vaccine and who need a booster would benefit more from an additional J&J vaccine, or should receive a different type of vaccine.
Currently, the official position of the CDC is that people should stick with the vaccine they initially received.
There is not enough data to know if the vaccine combination works and is safe.
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However, in some parts of Europe, doctors are mixing and matching AstraZeneca's single-dose vaccine, which is similar to the J&J vaccine, with an mRNA vaccine.
In Germany, health authorities recommended that people who received a first dose of the AstraZeneca vaccine receive an mRNA vaccine for their second dose.
The first studies showed that the mixture generated a strong immune response.
In June, German Chancellor Angela Merkel took the initiative and got the Moderna vaccine after her first dose of AstraZeneca.
Merkel was vaccinated with doses from different laboratories 0:44
In the United States, at least one city did not wait for data on the advisability of boosting the J&J vaccine.
People vaccinated with the J&J vaccine can receive a supplemental dose of the mRNA vaccine in San Francisco, where officials from the Department of Public Health made an "accommodation" for those who have seen a doctor, the department said Aug. 4. .
While Schaffner enthusiastically encourages those who have not yet been vaccinated for the first time to do so immediately, patients who have been vaccinated with J&J and want a booster are advised to be patient.
"For now, all we can tell you is to stay calm," Schaffner said.
"More information is on the way."
- CNN's Kaitlan Collins contributed to this report.
Covid-19 vaccines