On Tuesday, pharmaceutical company Moderna announced promising early results from the phase three trial of its potential COVID-19 vaccine - the third vaccine developer to do so in the past week.
Last week New York-based Pfizer and Germany's BioNTech became the first to release data based on large human trials, saying its vaccine - BNT162b2 - appeared to have 90 percent effectiveness at stopping infections of the SARS-CoV-2 virus which causes COVID-19.
Russia's Gamaleya Research Institute of Epidemiology and Microbiology quickly followed up with claims its Gam-COVID-Vac - nicknamed 'Sputnik V' - vaccine had 92 percent effectiveness. On Tuesday (NZ time) Moderna trumped them both, claiming 94.5 percent effectiveness.
Here's how each of them compare.
Claimed effectiveness
Experts said a 50 percent effectiveness - similar to that of influenza vaccines - would have been enough to get a particular vaccine approved, if it was also shown to be safe. But all three that have published data from their phase three trials appear to have cleared that hurdle with ease.
- Pfizer's BNT162b2 - 90 percent
- Russia's Gam-COVID-Vac - 92 percent
- Moderna's mRNA-1273 - 94.5 percent
Each of these results is based on interim data, and subject to change.
BNT162b2's 90 percent figure is based on 94 cases detected in a phase three trial involving more than 40,000 people. It's not clear if it protects against severe infections, University of Oxford public health expert Peter Drobac told The AM Show last week.
Gam-COVID-Vac's 92 percent figure is based on only 20 confirmed infections out of 36,000 participants - 18 infections in the control group and two in those who received the vaccine. While promising, experts expressed concern about inconsistencies in the little data supplied by Gamaleya, and whether its announcement was rushed after Pfizer made its announcement. Officials have only promised up to two years' protection, though it's not clear how long any of the vaccines will offer protection for.
mRNA-1273's 94.5 percent figure is based on 95 infections from 30,000 participants - 90 in the control group and five in those who got the jab. It appears to work just as well in the elderly, who are particularly vulnerable to COVID-19. The trial has also so far recorded 11 severe infections - all in people who didn't get the vaccine.
"This suggests that mRNA vaccines may prevent not only mild COVID-19 disease, but also more serious cases," said Fran Priddy, clinical director of Vaccine Alliance Aotearoa New Zealand. "We don't have these details regarding the Pfizer vaccine yet but it's reasonable to assume it will have the same benefit."
How they work
BNT162b2 and mRNA-1273 are both based on a relatively new technology called messenger RNA (mRNA).
In traditional vaccines, the body is injected with antigens - weakened or inactive viruses or their proteins - the immune system learns what it looks like, so when the live virus arrives the body reacts quickly to neutralise the threat. The antigens have to be grown beforehand. This is how Gam-COVID-Vac works, and it's proven technology that has been used to fight diseases such as smallpox, measles, mumps and rubella.
In mRNA vaccines, the body is injected with strands of genetic material coded to create the antigen, which is then produced by the body's own cells. The patient isn't injected with anything from the original pathogen. No existing vaccines use mRNA technology, which has been in development for about 30 years.
Cost
While the Moderna vaccine mRNA-1273 appears, based on early data, to be the most effective, it's also the most expensive of the three. Moderna earlier this year estimated it would cost about US$38 a dose. This could come down with bulk orders and as the technology improves. Pfizer has priced its vaccine at about US$20.
Both mRNA vaccines have been developed by private companies, who'll be seeking at least some profit for their investments.
Russia has said Gam-COVID-Vac would be cheaper than other vaccines, seeking to cut deals with poorer nations, like India and Brazil, but hasn't set a price.
Storage
While Pfizer was first out of the gate with its results, it has a problem - its vaccine has to be kept at a chilly -70C at all times to stay effective. Moderna's can be shipped at -20C, kept in a fridge for up to 30 days and at room temperature for 12 hours.
"These factors, while useful in high-income countries, will be of great value in low- and middle-income countries where there is a massive need for a vaccine that is able to be delivered to the population," said Prof Stephen Evans of the London School of Hygiene & Tropical Medicine.
Gam-COVID-Vac has to be kept frozen at -18C.
Funding
Gam-COVID-Vac is backed by the Russian Direct Investment Fund, the nation's sovereign wealth fund.
Moderna, a private company, has received funding as part of the US Government's 'Warp Speed' programme to hasten the arrival of a COVID-19 vaccine, as well as private investment.
Pfizer has not received any taxpayer cash, but its partner BioNTech got €375 million from the German government.
Track record
Pfizer has been around since the mid-19th century, and has existing vaccines for a range of illnesses.
Moderna was formed in 2010, focusing exclusively on mRNA vaccine technology, and has yet to have a single vaccine approved for use. Between its IPO in 2018 and the start of 2020, its share price hovered between US$13 and US$20 - it's since shot up to US$98, valuing the company at US$38 billion.
Little is known about the state-controlled Gamaleya Research Institute of Epidemiology and Microbiology outside of Russia. It was once private, but nationalised in the early days of the Soviet Union. Its director told The Financial Times in August they'd been working on adenoviral vaccine technology since the 1980s.
Others
These aren't the only three vaccine candidates in the works - there are more than 300, according to journal Nature Reviews Drug Discovery. At least seven others are in phase three trials, including efforts by the United States' Johnson & Johnson and Novavax, China's Sinovac and a joint effort between the UK's University of Oxford and AstraZeneca.
New Zealand's COVID-19 Vaccine Corporation is developing a vaccine based on homegrown bio-bead technology, which would be inexpensive to produce and easy to transport. Human trials aren't expected until later next year.
