Last week’s addition of two more effective vaccines against Covid-19 was very good news. With fast-spreading and potentially more virulent variants of the virus now on the rampage in many parts of the world, and grim predictions that some developing countries might not get adequate supplies of vaccines before 2023, we need all the prophylactic agents we can get against this pandemic.
But the positive news came with caveats. In particular, the effectiveness of both new vaccines is significantly lower against the fast-spreading South African virus variant denoted B.1.351. A trial of the US biotech company Novavax’s vaccine conducted in the UK on around 15,000 people showed it to be 90 per cent effective. That result, which will include protection against the new B.1.1.7 variant that accelerated the British second wave in the autumn, is great—not least because B.1.1.7 might cause more serious illness as well as spreading faster, and because some experts predict it will soon dominate infections in the US and elsewhere. But a smaller trial of the Novavax vaccine in South Africa gave only 49 per cent protection on average, which puts it close to the minimum threshold for an effective vaccine defined by the World Health Organisation.
“It was fortuitous to have these two trials in the UK and South Africa that we can compare in this way,” says biostatistician Natalie Dean of the University of Florida. The lower rate of success for the South African variant is troubling, she says, but we must “prepare to expect the unexpected, and we may need to update and adapt our strategy, and see how other vaccines fare in the same settings.”
Another bit of bad news from the South African trial is that some of the people who received a placebo instead of the vaccine and subsequently became infected had contracted the virus previously. It seems that infection with an earlier variant of the virus did not necessarily confer immunity against the new variant.
The other new vaccine comes from the American pharmaceuticals giant Johnson & Johnson. It showed 72 per cent protection in a US trial, and 66 per cent in Latin America. But against the B.1.351 variant in South Africa, this protection fell to 57 per cent. One great virtue of this vaccine is that it needs only a single shot, rather than the two required of the vaccines currently in use (and the Novavax vaccine), and there’s some evidence that the immune response gets stronger over time for two months or so. Also, it does not require cryogenic (very-low-temperature) storage: it keeps for a long time in a normal refrigerator. It is relatively cheap, and the company says it ultimately hopes to be able to produce a billion doses a year. Immunologist Akiko Iwasaki of Yale University told the New York Times that the announcement is “a really great result.”
Neither of the two new vaccines has yet received approval for rollout, but that is expected to happen very soon in many countries using Emergency Use drug-licensing provisions. Both new vaccines benefited from Operation Warp Speed, the US initiative to pour billions of dollars into Covid vaccine research. There are several others in development and use, such as those made by the Chinese company Sinovac, the Russian Sputnik V vaccine, and that from India-based Bharat Biotech.
Both of the new vaccines are more traditional than the mRNA vaccines that first received approval in December from US-based Moderna and from Pfizer and German company BioNTech. Like all the other vaccines so far, they raise an immune response in the body by presenting it with the “spike” protein through which the coronavirus latches onto and invades human cells. The differences lie in how the spike protein is made. The Novavax vaccine consists of a synthetic virus-sized particle studded with ready-made spike proteins, produced in the lab by using another virus to inject a piece of coronavirus DNA into moth cells. The vaccine also contains a chemical extracted from a plant which acts as an “adjuvant”: an additive of the sort commonly used in other vaccines, which boosts the immune response so that the body of a vaccinated person produces abundant antibodies that will recognise the spike protein and thus trigger an immune attack on the coronavirus itself.
The Johnson & Johnson vaccine, meanwhile, contains that spike-protein-encoding DNA itself. Here it is packaged inside another virus, called an adenovirus, that normally causes an ordinary cold but which has been inactivated so that it can’t itself replicate and cause illness. Once the modified adenovirus has carried the DNA strand into the cells of the vaccinated person, they start to produce the spike protein. This approach of using inactivated adenoviruses to deliver genetic material encoding the “antigen” that creates an immune response has long been developed by Johnson & Johnson and others for vaccines, in particular against Ebola (J&J’s was approved in Europe last July) and HIV.
A vaccine efficiency of, say, 90 per cent means that nine out of ten people who have been vaccinated will not develop Covid symptoms. In general, even those vaccinated individuals who do develop the disease will suffer milder symptoms. It is not yet clear if those who are protected from illness could nevertheless still be infected and transmit the virus to others, although it seems probable that if the vaccine hinders the virus from replicating in the body, a lower “viral load” makes transmission less likely. One heartening outcome is that the Johnson & Johnson vaccine seems particularly effective in suppressing serious Covid in all people: even those that still get it do so only mildly, and there were no fatalities among vaccinated participants in the trials.
Reduced effectiveness against the South African B.1.351 strain is likely to be common to all vaccines so far—both Moderna and Pfizer-BioNTech have reported this too, although results of tests with the vaccine made by AstraZeneca in collaboration with a team at Oxford University have not yet been released. But even an efficiency of 60 per cent or so can be enough to bring a pandemic under control, since it greatly reduces the chance of encountering an infected individual. “50 per cent, 90 per cent—it all helps,” says Dean.
Lets hope it will, for news has just emerged that the B.1.1.7 variant in the UK seems already to be acquiring one of the genetic mutations seemingly responsible for some of the reduced vaccine efficacy against the South African variant. As Kai Kupferschmidt, a reporter for Science magazine, has said, the latest results demonstrate why production of vaccines will need to evolve to keep pace with the virus’ own evolution and capacity to evade them—which means “we need to stop behaving as if vaccines alone will solve things.” They are vital tools to bring the disease under control, but need to be accompanied by ongoing measures to reduce transmission—and ultimately, to suppress it altogether, so that dangerous new variants can’t get a foothold. There’s cause for optimism, but this story won’t be over for a very long time.
