COVID-19 update from the CDC: What clinicians need to know about the vaccines
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On Friday, December 18, three physicians from the U.S. Public Health Service joined forces to present a webinar devoted to what clinicians across the healthcare continuum need to know about the two new COVID-19 vaccines now being distributed across the country. Amanda Cohn, MD; Sarah Mbaeyi, MD, MPH; and Sara Oliver, MD presented on behalf of the Centers for Disease Control (CDC) and Prevention’s Center for Preparedness and Response. It was a very informative hour made even better by a couple of itinerant barks from one of the presenter’s dogs, which left me with the comfort of knowing that I am not the only speaker of late experiencing unanticipated background noise while presenting from home. I’ve taken the information shared during the CDC webinar and developed a written summary of the content. In this digest, I hope to provide busy clinicians who may not have had time for the webinar with useful information about the available vaccines, how they work, precautions for patients, and how information should be shared with patients in the coming days, weeks, and months.
The vaccine developed by Pfizer-BioNTech received emergency use authorization on December 11, 2020. The Moderna vaccine received emergency use authorization on December 18 — bringing the number of approved vaccines in the U.S. to two with several more waiting in the wings. Both of the emergency use vaccines are what is known as messenger RNA (mRNA) vaccines and both have a reported effectiveness, across age, racial, and ethnic groups in the range of 94-95%. Both rely on two doses given a number of days apart for maximum effectiveness — 21 days for Pfizer-BioNTech, 28 days for Moderna. The spacing of doses has more to do with how the clinical trials were set up than any scientific rationale for setting the dosing. Both products have been demonstrated to be safe even though Dr. Cohn did identify an “imbalance” of Bell’s Palsy among some who participated in the clinical trials. She also stated that the side effect was still within an expected range of acceptability. With both vaccines, the presenters also suggest that those who are vaccinated can expect local and systemic reactogenicity, especially following the second dose. While the Pfizer-BioNTech vaccine must be stored at extreme freezing temperatures, the Moderna vaccine will be sustainable with refrigeration which will make it easier to deliver to areas of the country or locales where the right kinds of freezers are not present or are in short supply. Because of precautions against potential severe allergic reactions, patients who have been vaccinated should be observed for between 15 and 30 minutes following the injection depending on risk for an allergic response.
What exactly is mRNA, and how does it work?
Messenger RNA is a single-stranded RNA molecule that is compatible with a gene’s DNA strand. It isn’t the same as DNA, and it does not combine with a person’s DNA to alter genetic code as some who are skeptical of the vaccines have suggested. It also has a very short life span and will only last for a couple of days in one’s body — just long enough to do its work before being degraded. But, while there, good things are possible. In simple terms, here is how it works:
First, we know that the coronavirus injects itself into the cells of a person who becomes infected. As a person becomes infected, viral “spike” proteins are manufactured by the body and these spike proteins enable the virus to spread throughout the body by penetrating cells en masse.
The mRNA vaccine essentially provides instructions to the immune system by coding for the spike protein and producing an immune response that is similar to what would happen if a person were actually exposed, except the mRNA vaccines have no live virus and cannot interact with or integrate into the vaccinated person’s DNA. The spike protein mRNA and lipid particulate matter are the predominant ingredients in the vaccines along with buffering salts and sugars.
The lipid particles allow the vaccine’s mRNA to travel to the lymph system and enter antigen producing cells. The mRNA instructions are assimilated by the cell, and the spike protein is produced on the surface of the cell. Once that happens, the mRNA and lipids break down quickly. As the spike protein is produced on the surface of the antigen producing cell, a B cell neutralizing antibody response occurs. At the same time, CD4 and CD8 T cells are produced and create the response that establishes the body’s immune ‘memory.’ Thus, the mRNA vaccine works by enabling the body to mount a specific immune response to the virus through the creation of the B and T cells even though the virus itself is not present as a result of the vaccination.
What is in the vaccines?
The ingredients of the two vaccines from Pfizer-BioNTech and Moderna are similar, but not the same — as the table below shows. It will be important for clinicians to know these ingredients to ensure that patients who will be vaccinated do not have known severe allergic reactions to any ingredient.
Clinical considerations
Both vaccines have been approved for emergency use by the U.S. Food and Drug Administration (FDA). The Pfizer-BioNTech vaccine is approved for use in persons 16 and older, while the Moderna vaccine is approved for use in persons 18 and older. Healthcare staff members — those on the front lines — and residents of long-term care facilities are to be the first recipients of the vaccines. Other groups will be prioritized later in December.
The CDC has published clinical considerations for using the Pfizer-BioNTech vaccine, and the Advisory Committee for Immunization Practices (ACIP) of the CDC has published detailed best practice guidelines which outline in 196 pages a variety of recommendations that address scheduling, dose spacing, contraindications and precautions, risk considerations, infection control, alleviation of discomfort, storage and handling concerns, special situations, and maintenance of vaccination and event records. I encourage you to read the guidelines in their entirety with the understanding that a similar document aimed at the Moderna vaccine is expected from the CDC shortly. In this document, I’ll explore some of the interim clinical considerations for the Pfizer-BioNTech vaccine.
Pfizer-BioNTech guidance
- Doses and timing
The vaccine series is comprised of two doses (0.3 ml each) administered intramuscularly, three weeks apart. There is a grace period of 4 days between days 17 and 21 when doses are considered valid. If the second dose is given before day 17, it does not have to be repeated. If more than 21 days have elapsed since the first dose, the second dose should be given as early as possible, but the series does not need to be repeated. As I understand it, the spacing recommendations simply coincide with the clinical trial and are not cast in stone.
- Interchangeability
The Pfizer-BioNTech vaccine is not interchangeable with any other COVID-19 vaccine product. The safety and efficacy of a mixed product series have not been evaluated. If, inadvertently, two doses of different COVID-19 vaccines are administered, no additional doses of either vaccine are recommended.
- Concurrent vaccinations
The Pfizer-BioNTech vaccine should not be co-administered with other vaccines, such as a flu vaccine. There should be a minimum of 14 days between vaccination with the Pfizer-BioNTech vaccine and any other inoculation, but if the spacing is not adhered to, doses do not need to be repeated.
- Prior infections
Data suggests that the vaccine is safe in persons with evidence of a prior COVID-19 infection, and vaccines should be offered regardless of a history of prior symptomatic or asymptomatic infection. However, vaccinations for people with a known and ongoing COVID-19 infection should be deferred until the person has recovered and meets the criteria for discontinuation of isolation measures. Those who have been infected within the preceding 90 days may delay vaccination for a period of 90 days.
- Safety with antibody treatment
No data exists concerning the safety of the Pfizer-BioNTech vaccine for people who received monoclonal antibodies or convalescent plasma as part of treatment for COVID-19. Based on the estimated half-life of those therapies and evidence of reinfection, vaccination should be deferred for at least 90 days to avoid interference with the antibody treatment.
- Post-exposure considerations
No data is available for post-exposure prophylaxis, and protection from this vaccine is not immediate as it takes between one and two weeks after the second dose for a person to be considered fully vaccinated and sufficiently immune. Because the incubation period for COVID-19 is four to five days, current thinking is that vaccination is unlikely to be an effective strategy for preventing disease as a result of a prior exposure. Also, the CDC points out that people in the community with known COVID-19 exposure should not seek vaccination until after their quarantine period has ended to avoid inadvertent exposure of healthcare workers who are administering vaccines. The exception is for people residing in congregate living settings where exposure and transmission can occur repeatedly over long periods of time and where healthcare workers are already in contact with residents.
- People with underlying conditions
The Pfizer-BioNTech vaccine may be administered to those with no vaccination contraindications. Although people with stable HIV were included in the clinical trials, we do not currently have adequate data on the vaccine’s effectiveness for patients with HIV or other immunocompromising conditions. People in this group should be counseled about unknowns of vaccine safety and effectiveness.
- Pregnancy
Pregnant women and their healthcare providers should consider the level of COVID-19 risk and the lack of data concerning vaccine risk to those who are pregnant. Pregnant women who do take the vaccine may be advised to use acetaminophen in the event of post-vaccination symptoms. For those women who are trying to become pregnant, there is no need to avoid pregnancy after being vaccinated.
- Lactation
There is no data on the safety of the vaccine in lactating people or the effect of the vaccine on breastfed infants although the vaccine is not thought to be a risk to breastfeeding infants.
- Vaccination of adolescents
Children between the ages of 16 and 17 can receive the Pfizer-BioNTech vaccine under the emergency use authorization as there were no safety concerns identified during clinical trials.
- Patient counseling
Available data suggests that the Pfizer-BioNTech vaccine is 95% effective following the second dose. Patients should be counseled on the importance of follow–up and receiving the second vaccine dose once the series is started.
- Reactogenicity
Prior to being vaccinated, all patients should be counseled about expected local side effects including pain at the injection site and post-vaccination symptoms such as fatigue, headache, chills, myalgia, and arthralgia. About 85% of those vaccinated during the clinical trials developed at least one local injection site symptom, and 77% developed at least one systemic symptom. Most were mild and resolved within one to two days; however, symptoms were more frequent and more severe following the second dose and among younger people, including those between the ages of 18 and 55. Patients should be encouraged to complete the series unless a significant contraindication develops. While anaphylaxis was not observed during the clinical trials of the vaccine, it has been observed during mass vaccination outside of the trial. Antipyretic or analgesic medications may be taken for the treatment of post-vaccination local or systemic symptoms, but prophylactic administration of such medications to prevent post-vaccination symptoms is not recommended.
- Public health recommendations
Information about the degree to which the vaccine may reduce transmission in the general population and how long that protection will last is limited. As a result, vaccinated people should continue following all current CDC guidance to protect themselves and others including wearing a mask, social distancing, hand hygiene, and avoiding crowds.
- Contraindications
A severe allergic reaction to any ingredient of the Pfizer-BioNTech vaccine is a contraindication to vaccination. Anaphylactic reactions in persons outside the clinical trials have been reported and are being investigated. In the meantime, the CDC considers a history of severe allergic reaction to any other vaccine or injectable suggestive of a precaution but not a contraindication to vaccination. In such cases, a risk assessment should be conducted to determine the type of reaction and possible causes. A history of mild vaccine reaction without anaphylaxis is not a contraindication to the vaccine. Additionally, allergies such as reactions to medications other than vaccines or allergies related to foods, pets, venom, environmental, or latex allergies are not considered contraindications to vaccination. Nonetheless, appropriate medical treatment used to manage immediate allergic reactions must be immediately available as injections of the vaccine are being given.
- Adverse events
Adverse events related to vaccination of a person should be reported through the Vaccine Adverse Event Reporting System (VAERS). Vaccination providers are required by the FDA to report certain events including vaccine administration errors, serious adverse events, cases of multisystem inflammatory syndrome, and cases of COVID-19 that result in hospitalization or death. The CDC has developed a new smartphone tool called v-safe. The tool uses text messaging and web surveys to provide health check-ins after patients are vaccinated. Reports of significant health impacts are followed up by the CDC through v-safe to collect additional information and for completion of a VAERS report.
The following table summarizes triage for persons presented for Pfizer-BioNTech vaccinations.
Moderna clinical guidelines coming soon
The CDC has not yet published clinical guidance for the Moderna vaccine as it was just approved for emergency use by the FDA; however, the FDA does have an advisory notice for use by providers.
Doses and timing
The Moderna vaccine is administered intramuscularly as a series of two dozes of 0.5ml each with one month between the first and second dose.
Contraindications
The Moderna vaccine should not be administered to individuals with a known history of severe allergic reaction, such as anaphylaxis, to any ingredient of the vaccine. Appropriate medical treatment to manage allergic reactions must be immediately available in the event of an acute anaphylactic reaction following vaccination. Vaccine recipients must be monitored for adverse reactions based on guidelines from the CDC. Moderna also notes that immunocompromised persons, including those receiving immunosuppressant therapy may have a diminished immune response to the vaccine. Further, the vaccine may not protect all recipients.
Adverse reactions
Adverse reactions were reported during the clinical trial of the vaccine and included pain at the injection site, fatigue, headache, myalgia, arthralgia, chills, nausea/vomiting, axillary swelling and tenderness, fever, swelling at the injection site, and erythema.
Concurrent vaccinations
There is currently no information available on the administration of the Moderna vaccine with other vaccines.
Underlying conditions
Patients should be asked about the existence of allergies, recent fever, bleeding disorders or use of blood thinners, whether they are immunocompromised or on medicine that affects the immune system, pregnant or planning to become pregnant, breastfeeding, or have received another COVID-19 vaccine. Those who have experienced an allergic reaction to a previous dose of the Moderna vaccine or who have had a severe allergic reaction to any ingredient of the vaccine should not be given the vaccine.
Recommended medications and supplies for vaccination sites
*Antihistamines may be given as adjunctive treatment, but should not be used as an initial or sole treatment for anaphylaxis. Caution should be used if oral medications are administered to persons with impending airway obstruction.
In the case of an adverse reaction necessitating the administration of epinephrine, clinicians should immediately call 911. The speakers during the webinar also noted that, in some settings and with some patients, anaphylaxis may be difficult to immediately recognize — for example, in long-term care settings with elderly patients who may be affected by dementia. If it is not clear whether the patient is having an anaphylactic reaction, the best course of action is to administer the epinephrine and then call 911, but caution should be exercised as some patients with cardiac conditions can have side effects from the epinephrine. Consequently, the ability to rapidly understand the nature of the patient’s reaction to the vaccine and the best course of action will be important. Clinicians should also know that anaphylaxis is rare and occurs in only one of more than 1.3 million vaccinations.
Resources
The CDC has published several resources for clinicians and providers, and more are coming. Here are some that readers may want to investigate:
Additional toolkits expected to be available soon will address vaccination management and clinical issues in long-term care facilities, health departments, community-based organizations, and for employers of essential workers.
In closing
The CDC’s December 18 webinar “What Clinicians Need to Know About the Vaccines” was useful and informative. Click here to watch the webinar on-demand.
I’m getting more and more comfortable with the need to get this vaccine when my group comes up. We should all be sincerely grateful for the prioritization of those on the front lines and our most vulnerable patients. As they say… together, we can do this.