Key points
There is a safe and effective vaccine that has been approved by the U.S. Food and Drug Administration (FDA) to prevent Ebola disease. This vaccine is called ERVEBO® and is only effective against one of the viruses cause Ebola disease. ERVEBO should only be given to patients who meet specific criteria. Healthcare providers should consider contraindications, precautions, and considerations for specific populations before administering the vaccine.
Overview
ERVEBO is approved by the U.S. Food and Drug Administration (FDA) for the prevention of disease caused by Ebola virus (species Orthoebolavirus zairense)) in individuals 12 months of age and older as a single dose administration. ERVEBO is manufactured by Merck.
ERVEBO is a replication-competent, live, attenuated recombinant vesicular stomatitis virus (VSV) vaccine. It is not possible to become infected with EBOV from the vaccine. The vaccine only contains a gene from the Ebola virus, not the whole virus.
Recombinant vaccines, like Ervebo, act like a natural infection, so they're especially good at teaching the immune system how to fight germs. The Ervebo vaccine is made by taking a small piece of the Ebola virus and adding it to the vesicular stomatitis virus, forming what is referred to as the "vaccine virus". Because the vaccine virus only contains a small piece of the Ebola virus, not the whole virus, the vaccine cannot make someone sick with Ebola.
ERVEBO does not provide protection against other species of orthoebolaviruses or orthomarburgviruses.
Reminder
Vaccinated laboratory staff and healthcare workers at risk for occupational exposure to Ebola virus must continue to adhere to biosafety guidelines and infection prevention and control procedures.
Vaccinated Ebola disease outbreak responders must wear recommended personal protective equipment and follow proper procedures to prevent infection.
Efficacy
Clinical efficacy of the vaccine was supported by a randomized cluster vaccination study during the 2014–2016 outbreak in Guinea. In this study, 3,775 people in close contact with someone diagnosed with Ebola disease and their close contacts received immediate vaccination with ERVEBO. No one who was vaccinated immediately developed Ebola disease 10 or more days after vaccination.
Precautions and contraindications
During the clinical development of the vaccine, there were two reports of serious vaccine-related pyrexia and two reports of non-fatal anaphylaxis. Following vaccination, administering healthcare providers should monitor vaccinated individuals for signs and symptoms of hypersensitivity reactions. Appropriate medical treatment and supervision must be available in case of an anaphylactic event following the vaccine administration. Each vaccinated individual should be observed for a minimum of 15 minutes following vaccination.
Immunocompromised individuals
Vaccination with ERVEBO may not protect all individuals. Its safety and effectiveness have not been assessed in immunocompromised people and the vaccine may be less effective in this group.
To date, a small number of HIV-positive adults have been vaccinated in a trial in Liberia, under the Partnership for Research on Ebola Virus in Liberia (PREVAIL). Additional studies are ongoing to evaluate the vaccine's use in HIV-positive individuals who are not severely immune-compromised. The risk of vaccinating immunocompromised people with a live virus vaccine should be weighed against their risk of Ebola disease.
Allergies
Because ERVEBO is produced with rice-derived recombinant human serum albumin, precautions should be taken with individuals allergic to rice. People with a history of severe allergic reactions such as anaphylaxis to rice protein should not receive this vaccine.
Presence of VSV RNA post vaccine
Attenuated VSV vaccine virus RNA has been detected by reverse-transcription polymerase chain reaction (RT-PCR) in urine up to seven days post-vaccination, in blood and saliva up to 14 days post-vaccination, and in fluid from skin vesicles up to 20 days post-vaccination. Transmission of vaccine virus through personal contact is theoretically possible. Healthcare providers administering vaccine should exercise appropriate infection control practices.
Vaccine recipients should avoid:
- Sharing needles, razors, toothbrushes, eating utensils, drinking from the same cup, and open mouth kissing for two weeks after vaccination. If oral sores develop after vaccination, vaccine recipients should avoid these activities until the sores heal.
- Contact and association with immunocompromised individuals, pregnant or breastfeeding people, and children less than 1 year of age for up to six weeks following vaccination.
- Exposing livestock to the recipient's blood and body fluids for up to six weeks following vaccination.
ERVEBO® should not be given to people with any of the following:
- Known severe allergy, such as anaphylaxis, to any component of the vaccine, including rice protein.
- Clinical evidence of a systemic infection or other acute intercurrent illness at the scheduled time of vaccination (e.g., oral temperature >38°C [100.4°F], systemic symptoms). Vaccination may be rescheduled later if the conditions resulting in ineligibility are no longer present.
- Presence of any clinically significant medical condition, past medical history, pre-existing illness (e.g., acute malignancy, history of Guillain-Barré syndrome, history of neurologic disorder that may increase risk, active autoimmune disorder or immunosuppression) that may place the individual at an increased risk of a serious adverse event following vaccination.
While pregnancy and lactation are not absolute exclusion criteria for receiving ERVEBO, live attenuated vaccines are generally contraindicated during pregnancy. Women of reproductive age should be counseled on the potential fetal risks of vaccination. Determination of whether to receive the vaccine should be made on an individual basis, in consultation with a healthcare provider, based on the benefit/risk of vaccination against the risk of exposure to Ebola virus.
Considerations for specific populations
Pregnancy
There are no well-controlled studies of ERVEBO in pregnant people. Data available from human clinical trials are not sufficient to establish whether the vaccine poses a risk during pregnancy. In a randomized, unblinded vaccine study in Sierra Leone, there were no statistical differences in pregnancy loss among those who were vaccinated against Ebola virus versus those unvaccinated. Likewise, there were no external congenital abnormalities among babies born to people who were part of the vaccine study.
The World Health Organization recommends the use of ERVEBO in pregnant and breastfeeding people in areas experiencing an active Ebola disease outbreak, in the context of rigorous research or through a compassionate use protocol. The risk of exposure to Ebola should be weighed against potential vaccine-related risk during pregnancy based on individual informed decisions.
Lactation
Data are not available to assess the impact of ERVEBO on breast milk, its effects on the breastfed child, or on milk production. The child's development and the health benefits of breastfeeding should be considered along with the mother's clinical need for the vaccine. Any potential adverse effects on the breastfed child from the vaccine or from the mother's risk to Ebola virus should also be considered.
Older Adults
A total of 542 older adults received the Ebola vaccine during clinical trials. Although this was inadequate to determine whether the immune response in older adults (≥ 65 years) is different from younger participants, the FDA-approval of ERVEBO for prevention of disease caused by EBOV in adults (≥ 18 years) is inclusive of older adults without an upper age limit.
Reporting adverse events
To report suspected adverse reactions, contact Merck Sharp & Dohme LLC at 1-877-888-4231 or VAERS at 1-800-822-7967 or Vaccine Adverse Event Reporting System (VAERS) (hhs.gov).
Overall, reported vaccine-related severe adverse events (SAEs) were rare. Across 12 studies, out of 15,399 people who received the vaccine, three SAEs were judged to be related or possibly related to the vaccine: one febrile reaction, one anaphylactic reaction, and one influenza-like illness. An additional case of anaphylaxis was identified in data provided to FDA. All resolved without sequelae.
See package insert for more information on adverse events.