The race for gold: Closing in on the first RSV vaccine

starting line

The industry looks set to bring the first vaccine for RSV to market in the coming year. Ben Hargreaves finds out which companies are leading the race, and why it would mark an important development for global health.

One of the greatest achievements of modern medicine has been the dramatic fall in infant mortality rates. In just over a century, the infant mortality rate in the US declined from 165 per 1,000 to the current rate of 5.4 per 1,000. Globally, the rates have dropped by more than half in the last thirty years. Reducing levels by such an amount has required hitting the largest causes of death, and the next major target is respiratory syncytial virus (RSV). The virus is the second leading cause of infant death globally, only behind malaria. The infectious disease also poses a threat to the health of older adults.

This is why a new generation of vaccines and treatments emerging against the virus is creating hope that children and older adults may soon be able to be effectively protected. Already, Sanofi and AstraZeneca’s monoclonal antibody to protect infants against RSV has been given approval in Europe, under the brand name Beyfortus (nirsevimab). The treatment is also under review by the FDA, with a decision date set to be made in the third quarter this year. 

Also being examined by the FDA are two vaccines that could soon receive approval against RSV, in the form of Pfizer’s and GSK’s vaccine candidates. Behind these options, there is a growing pipeline, with a number of companies looking to advance their own candidates against the virus. If any should prove successful in gaining approval, the potential to aid global health could be enormous, and enormously lucrative to the company behind the vaccine.

The threat of RSV

RSV was first discovered in 1956, and currently causes annual outbreaks of respiratory illness in all age groups. For older children and most adults, the risks when contracting the virus are relatively small. Most people will present symptoms similar to a common cold, and will recover in a similar period of time. In infants and young children, however, it can pose more serious risks, particularly in those with suppressed immune systems or those with neuromuscular disorders. As mentioned, adults over the age of 65 are more likely to develop severe symptoms consistent with lower respiratory tract infections, such as pneumonia.

Globally, RSV affects an estimated 64 million people and causes 160,000 deaths each year. According to the World Economic Forum, case numbers have been on the rise in recent years, which is speculated to be due to children being shielded from the infection during COVID-19 lockdowns. As a result, there is more interest and demand for successful solutions to be developed.

Leading the pack

At the head of the pack for the latest generation of options are Pfizer’s and GSK’s candidates. Both recently managed to secure votes in favour of approval by the FDA’s advisory committee. In turn, this could see both gain full approval from the agency during the course of 2023. Any approval will prove to be a landmark in the field for RSV prevention, as there are currently no RSV vaccines available.

In clinical trials, Pfizer’s potential vaccine showed a 66.7% efficacy in preventing RSV-related lower respiratory infections with two or more symptoms, and 85.7% efficacy against three or more symptoms. This trial was related to the vaccine’s use in adults 60 years and older. In further phase 3 trials, the vaccine was 81.8% effective against severe medically attended lower respiratory tract illnesses when administered to pregnant participants to protect their infants against RSV. Substantial efficacy of the vaccine was determined to be 69.4% over a six-month follow-up period for infants.

By comparison, GSK’s vaccine candidate showed overall vaccine efficacy of 82.6% against RSV lower respiratory tract disease in adults aged 60 years and older. In tests to determine protection against severe RSV lower respiratory tract disease, the vaccine was 94.1% effective. In patients with comorbidities, the vaccine was 94.6% effective.

A challenging area

In terms of efficacy numbers, GSK’s vaccine candidate seems to hold an advantage over Pfizer’s rival vaccine. However, GSK was forced to halt trials into the potential vaccine’s use in pregnant women to protect their infants. According to the company, the decision was made as a result of safety data from the trials, but further details have not yet been revealed.

GSK is not the only company that has hit roadblocks on the road to developing a successful vaccine. Johnson & Johnson had also been well-advanced in taking its own potential vaccine through clinical trials, before it made the decision to discontinue its development. The vaccine had advanced into phase 3 studies before the decision was made, but this was deemed not enough for the company. In a statement at the time of the decision, J&J outlined that it had undertaken a review of its portfolio and decided to prioritise other assets for investment. The choice may have been made in light of needing to conduct a trial containing 27,000 people, which would have concluded next year. With both Pfizer’s and GSK’s vaccines potentially receiving approval this year, this would have left J&J’s vaccine candidate some way behind in the race to commercialise.

This does not mean there are no other competitors looking to advance other options for RSV, as Moderna was recently granted FDA breakthrough therapy designation for MRNA-1345, an mRNA RSD vaccine candidate. The company plans to file for regulatory approval in the first half of 2023, on the back of phase 3 data that showed vaccine efficacy of 83.7% in adults aged 60 and over. Bavarian Nordic is another company working on a vaccine and revealed mid-way through April that it had accrued sufficient cases to complete the primary efficacy analysis of its phase 3 trial.

The reason that there are such a number of companies competing to get their potential products onto the market as quickly as possible is due to the potential size of the market. Bloomberg Intelligence analyst, John Murphy, states that the market could be worth up to $8 billion. Pfizer has already said that it predicts peak sales of its vaccine could reach $2 billion. As a result, it is difficult not to see the efforts to gain approval against RSV as a race for gold.