Yesterday, CDC Director Rochelle Walensky, MD, MPH, announced the agency’s support for the use of Novavax’s COVID-19 vaccine as the primary series among people ages 18 and older. The new COVID-19 vaccine is being positioned as a more traditional platform than the mRNA technology and, as such, the agency hopes to interest those who are still unvaccinated.
Novavax is a protein subunit vaccine that delivers 5 mcg of the fully formed spike protein along with an adjuvant which focuses the attention of the innate immune system on the spike antigen. In contrast, the mRNA platform provides cells with the instructions to make the spike protein. Other vaccines which are based on a protein subunit are the hepatitis B, HPV, acellular pertussis (whooping cough) and shingles vaccines.
The primary series is two doses administered three to eight weeks apart for those who are not moderately or severely immunocompromised. A 3-week interval is recommended for those who are moderately or severely immunocompromised.
Boosters, mix-and-match, and timing with other vaccines
A booster dose is not currently recommended, nor is a mix-and-match approach currently advised for Novavax. If the FDA authorizes these adjustments, the ACIP can add such recommendations to the immunization schedule. Covid vaccines can, according to the ACIP, be administered with other routinely recommended vaccines. The only caveat is orthopox (Monkeypox) vaccination, after which a covid vaccination should be delayed for four weeks. If a person has received a Covid vaccine recently but needs orthopox vaccination due to an exposure, there is no need to wait.
Safety and efficacy data
The process of approving a new vaccine or drug product starts with Food and Drug Administration (FDA) review of clinical trial data, after which an Emergency Use Authorization (EUA) may be issued. The Advisory Committee on Immunization Practices (ACIP) then reviews the data and develops recommendations for CDC to adopt and share with the general public. This process was completed yesterday (July 19, 2022) with the ACIP’s unanimous vote in support of Novavax for use in adults.
The clinical trial for Novavax included people 18 years of age and older in the US and Mexico who had not previously been infected with Covid. The trial population was diverse, but the investigators noted that it was harder to enroll older individuals given that mRNA vaccines had just been made available.
Among those in the trial, 17,200 received the vaccine and 8,300 received the placebo. Investigators reported that the vaccine was 90.4% effective in preventing mild, moderate or severe COVID-19 and 100% protective against moderate or severe COVID-19. Among patients 65 years or older, efficacy was 78.6%. It should be noted that this data was gathered prior to emergence of the Delta and Omicron variants and real-world effectiveness now is likely lower. In addition to tracking effectiveness, additional post-authorization safety data will also be collected as the vaccine is administered among the general population.
Myocarditis (heart inflammation) is a rare but known adverse event of particular concern for young males in the first week after the primary series and booster mRNA vaccination. The spike protein antibodies produced by the immune system are thought to cross-react with cardiac muscle proteins causing inflammation. Patients who notice a fast beating, pounding heart and chest pain are advised to seek medical attention.
Myo/pericarditis is a concern for Novavax as well. The FDA briefing document indicates that the cardiac events which closely followed vaccination in the clinical trial were “potentially related” to vaccination. Safety data from Europe, included in the briefing document, also detected a statistical signal for myo/pericarditis with observed events exceeding the expected background rate. The manufacturer, CDC, and the FDA are conducting ongoing safety monitoring along with counterpart agencies abroad.
Other precautions due to allergies or illness
People who are allergic to polysorbate should not receive either Novavax or Janssen Covid vaccines. An allergy to polyethylene glycol (PEG) precludes mRNA vaccination. Precautions are advised for those who have had an immediate allergic reaction to any other non-Covid vaccine, moderate or severe acute illness with or without a fever, a history of MIS-C or MIS-A, or myo/pericarditis after mRNA vaccination.
Novavax during pregnancy and lactation
Although Novavax during pregnancy was not evaluated during the clinical trials, the WHO Strategic Advisory Group of Experts on Immunization (SAGE) recommends that pregnant women be counseled regarding the risks and benefits of vaccination, and that breastfeeding women accept vaccination. The CDC’s patient fact sheet asks women who receive Novavax during pregnancy to enroll in a pregnancy registry for follow-up.
Prior SARS-CoV-2 infection and vaccination
The CDC recommends vaccination for people who have been infected with SARS-CoV-2 previously, but waiting a few months after isolation ends may be helpful to boost the immune response. The CDC notes that the risk of reinfection is low in the weeks and months after infection. The WHO’s SAGE concurs that those who have been infected by COVID-19 recently wait three months prior to vaccination.
Having another option for COVID-19 vaccination may interest the 26 to 37 million US adults who have not yet been vaccinated. The protein subunit vaccine platform has been around for decades and Novavax has also been approved for use in Europe (as Nuvaxovid) down to age 12 since December 2021. The White House has procured 3.2 million doses for distribution in the coming weeks. Additional studies are ongoing to assess safety and effectiveness, and the company is testing vaccination for adolescents as well as a booster containing an Omicron component.