SHIRLEY DE VILLIERS: Covid vaccines: the good, the bad, and the unknown
Blimp of good news on the horizon as Covid vaccines hit the sweet spot
On the heels of Pfizer’s recent announcement that its Covid vaccine is 90% effective, US biotech upstart Moderna on Monday announced a 94.5% efficacy rate for its offering – only to have Pfizer rejoin with a 95% efficacy update on Wednesday.
The results from phase 3 clinical trials for both vaccines are promising. As health website StatNews reports, among Pfizer’s roughly 43,000 trial volunteers, 170 have so far presented with symptoms of Covid and tested positive for the coronavirus; 162 of those were in the placebo group, while just eight were in the group that received the double-dose vaccine. Of 10 severe cases of Covid, nine were in the placebo group.
The stats in the Moderna trial look much the same, as this useful Guardian explainer notes: 90 of the 95 cases of Covid reported among its trial volunteers were in the placebo group, as were all 11 severe cases.
In both trials, side-effects seem limited: pain at the site of the injection on receiving the first dose, and short-lived instances of fatigue and headaches.
It’s a wonder of science. Both vaccines are based on messenger RNA, or mRNA – a new way of thinking around vaccines. As The Atlantic’s Sarah Zhang explains in this most accessible read, traditional vaccines are developed from a weakened or inactive virus, or a piece of a virus, which stimulates an immune response in the body. It’s a time-consuming process in which scientists have to figure out how to make viruses.
By contrast, mRNA vaccines get the human body to do the heavy lifting.
Zhang writes: “When the coronavirus infects us, it hijacks our cellular machinery, turning our cells into miniature factories churning out infectious viruses. The mRNA vaccine makes this vulnerability into a strength.”
Essentially, mRNA carries information that allows cells to replicate the distinctive “spike protein” that covers the coronavirus. This modified mRNA is covered with fat and, when injected into the human body, “human cells take up this bubble and simply follow the directions to make the spike protein. The cells then display these spike proteins, presenting them as strange baubles to the immune system. Recognising these viral proteins as foreign, the immune system begins an arsenal to prepare for the moment a virus bearing this spike protein appears.”
So when coronavirus infection occurs, the immune system is already primed to recognise the invader, and deploy its weaponry.
The mRNA vaccine process mimics viral infection better than traditional vaccines do, Zhang writes, which could make it more successful. It also has a longer period in which to prod the immune system into action. mRNA vaccines can keep producing spike proteins for up to two weeks, American immunologist Drew Weissman tells her, where inactivated viruses and viral pieces usually disappear from the body in about a day.
There are other positives to take out of the vaccine developments. First, there’s the reported efficacy: the vaccine would seem not only to limit mild cases of Covid, but also the number of cases requiring hospitalisation.
As Zhang and The Guardian’s Nicola Davis note, the trials also suggest vaccines based on the spike protein work – which is good news for a number of the other vaccines in development, including the AstraZeneca product being trialled in SA.
And the two trials included participants across age and racial demographics – important where the virus is more severe for particular groups.
Success of mRNA vaccines could also revolutionise vaccination. For example, Zhang reports scientists are already working on an mRNA vaccine for the Zika virus, which if contracted during pregnancy can cause birth defects, and for which there is currently no vaccine.
Put the cork back in the bubbly
Like most good news, this all comes with a fair number of caveats. The Pfizer vaccine, for example, has to be stored at -80°C – which complicates the supply chain quite dramatically, and could make its rollout particularly problematic in underdeveloped countries.
The Moderna vaccine is more suited to easy distribution – it can be stored at between 2°C and 8°C for 30 days, and -20°C for up to six months. But it’s looking to be a lot more expensive. As The Guardian reports, the vaccine is set to cost $37 a dose, against an estimated $10 for a Johnson & Johnson vaccine in testing, and $20 for Pfizer’s offering. (Moderna has made no bones about making a profit off its vaccine – though it has reportedly agreed to suspend its patent rights for the duration of the pandemic.)
For now, the Moderna vaccine is also headed straight for the US market, after the company received $2.48bn from the US for development costs and the delivery of 100-million doses. The company is also reportedly in talks with the EU. So it will be a while before doses become more widely available.
Not that we know when SA is going to see a vaccine in any case. As Business Day’s Tamar Kahn reports, we’ve missed the October deadline for committing to Covax – a pooled purchasing agreement – and have yet to make any advance purchasing agreements directly with manufacturers. And we still don’t have a plan for how we will distribute vaccines when we get them (other than to frontline health-care workers).
Of course, this is one among a number of unknowns. For a start, the Moderna and Pfizer trials are not yet peer-reviewed and are not yet considered complete – so the results, while indicative, are not definitive.
As Davis’s explainer notes, we also still don’t know for how long the vaccines will be effective. And we don’t actually know whether the vaccines will just stop us from developing Covid symptoms, or whether they will prevent transmission too. (This can have important implications for how limited vaccines are distributed, as per this fascinating New York Times article.)
Still, there’s much to be positive about – at last.
For that, the world owes a debt of gratitude to Hungarian-born scientist Katalin Karikó, whose determination to keep pulling at the mRNa thread saw her demoted to “the lower rungs of the scientific academy”, as Damian Garde and Jonathan Salzman write in this long-form piece on the evolution of mRNA vaccines.
Moderna co-founder Derrick Rossi told Garde and Salzman he believes Karikó – and her associate Weissman – deserve the Nobel prize in chemistry for a “fundamental discovery” that will “go into medicines that help the world”.
Maybe now they’ll get it.
*De Villiers is the features editor of the FM
This is a roundup of the best Covid-19 news from the web, brought to you in today’s FM lockdown newsletter.
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