The Food and Drug Administration has authorized Novavax‘s two-dose vaccine for adults ages 18 and over, the fourth Covid shot to get emergency approval in the U.S. since the pandemic began.
The FDA decision comes weeks after its committee of independent vaccine experts voted overwhelming in favor of Novavax’s shot in early June, after an all-day public meeting in which they weighed data on the vaccine’s safety and its effectiveness at preventing illness from Covid.
The Centers for Disease Control and Prevention still needs to sign off on Novavax’s vaccine before pharmacies and other health-care providers can start administering shots. FDA authorization of Novavax’s vaccine was delayed for weeks as the agency reviewed changes to the company’s manufacturing process.
Novavax was one of the original participants in the U.S. government’s race to develop a Covid vaccine in 2020, receiving $1.8 billion in taxpayer funding from Operation Warp Speed. However, the small Maryland biotech company struggled to quickly get manufacturing in place and its clinical trial data read out much later than Pfizer or Moderna.
Novavax’s shots have received FDA authorization at a time when nearly 77% of adults ages 18 and over are already fully vaccinated. However, 27 million adults still have not gotten a single shot yet. Dr. Peter Marks, a senior FDA official, said Novavax’s vaccine would potentially appeal to unvaccinated people who would prefer a shot that is not based on the messenger RNA technology used by Pfizer and Moderna.
How Novavax is different
The Novavax shot is based on more conventional protein technology used for decades in hepatitis B and HPV vaccines, while Pfizer and Moderna are the first FDA approved vaccines to use mRNA.
Pfizer and Moderna’s vaccines use mRNA, a molecule encoded with genetic instructions, to tell human cells to produce copies of a virus particle called the spike protein. The immune system responds to these copies of the spike, which prepares the human body to attack the actual virus.
Novavax makes copies of the virus spike outside human cells. The genetic code for the spike is put into an insect virus that infects moth cells, which produce copies that are then purified and extracted during the manufacturing process. The finished spike copies are injected into the human body, inducing an immune response against Covid.
The Novavax vaccine also uses an additional ingredient called an adjuvant, which is extracted and purified from the bark of a tree in South America, to induce a broader immune response. The shots consist of 5 micrograms of the spike copy and 50 micrograms of the adjuvant.
Effectiveness and safety
Two doses of the Novavax vaccine were 90% effective at preventing illness from Covid across the board and 100% effective at preventing severe illness, according to clinical trial data from the U.S. and Mexico. However, the trial was conducted from December 2020 through September 2021, months before the omicron variant became dominant.
Novavax did not present any on data on the shot’s effectiveness against the variant at the FDA committee meeting in June. However, the vaccine will likely have lower effectiveness against omicron as is the case with Pfizer and Moderna’s shots. Omicron is so distinct from the original strain of Covid that the antibodies produced by the vaccines have trouble recognizing and attacking the variant.
Novavax published data in December showing that a third shot boosted the immune response to levels comparable to the first two doses which had 90% effectiveness against illness. The company plans to ask the FDA to authorize a third dose of its vaccine.
FDA authorization of Novavax’s vaccines comes as the U.S. is preparing to updated Covid shots to target the omicron BA.4 and BA.5 variants to increase protection against the virus. Novavax’s vaccine, like all the other shots, is based on the original version of the virus that first emerged in Wuhan, China. The effectiveness of Covid vaccines against mild illness has slipped substantially as the virus as evolved, though they still generally protect against severe disease.
Novavax presented data at an FDA committee meeting in late June demonstrating that a third dose of its vaccine produced a strong immune response against omicron and its subvariants. Committee members were impressed by the company’s data on omicron.
The Novavax vaccine also appears to carry a risk of heart inflammation for younger men, known as myocarditis and pericarditis, similar to Pfizer and Moderna’s shots. Myocarditis is an inflammation of the heart muscle and pericarditis is inflammation of the outer lining of the heart.
FDA officials flagged four cases of myocarditis and pericarditis from Novavax’s clinical trial in young men ages 16 to 28. People who develop heart inflammation as a side effect of Covid vaccines are usually hospitalized for several days as a precaution but then recover.
The FDA has issued a fact sheet for health-care providers warning that clinical trial data indicates there is an increased risk of myocarditis with the Novavax vaccine. People who experience chest pain, shortness of breath and feelings of a fluttering or pounding heart should immediately seek medical attention, according to the FDA.
In the case of the mRNA shots, the CDC has found that the risk of myocarditis is higher from Covid infection than vaccination. Myocarditis is usually caused by viral infections.