By Tim Harford, The Financial Times
In a situation where more than half of the British population has been fully vaccinated, and when the government is eager to declare victory, let me say 2 words about Cameroon. With a population as large as half that of England, Cameroon has administered only 160,000 doses of the vaccine. On a typical day, this amount is administered by the UK from breakfast until just before lunch.
I have a certain romantic connection with Cameroon, but the country located in West Africa is not the only one suffering from a lack of vaccines. More than 6 months after the launch of the global vaccination campaign, less than a quarter of people worldwide have received even a single dose of the vaccine.
It is therefore no surprise that more people have died from Covid-19 this year 2021 than in 2020. So what can be done in these conditions? There has been a lot of talk about equality in the distribution of vaccines, but the main problem is not the collection of vaccines or the rise in prices.
The problem lies with the manufacturers, who can not produce the doses they need so quickly. If they had the chance, then India, as a major vaccine producer in the world, would have fully vaccinated far more than just 5 or 6 percent of the population that has been vaccinated to date.
The global production of vaccines, however, has been impressive and at an accelerated pace. According to Airfinity, a life science analytics company, 1 billion doses were produced by April 12. Another billion were produced by May 26, and the third billion by June 22.
This is a very promising pace. But we need 11 billion doses to fully vaccinate 70 percent of the world, which may not happen until 2022. But lately, an idea that sounds almost childish is gaining traction: if we reduce the dose, we we can vaccinate more people from each vaccine vial.
And why not give people half a dose? What about a quarter dose? By a quarter dose, we could already have vaccinated the adult population of the world. The idea seems absurd at first glance – you can not get drunk diluting the beer you are drinking with water – but it all depends on how effective vaccines can be in lower doses.
Five years ago, faced with an epidemic of yellow fever and a lack of vaccines, 7 million people in the Democratic Republic of Congo each received only one-fifth of the normal dose. And that strategy approved by the WHO also seems to have worked.
Alex Tabarrok, a professor at George Mason University, has been promoting the idea of alternative vaccine dosing regimens for months. Recently, he and other researchers, including vaccine market specialist and Nobel Prize-winning economist Michael Kremer, made public a study on the subject.
At the same time, another study advocating a reduced-dose regimen, authored by epidemiologists Benjamin Coeling and Ëey Wen Lim, and virus evolution specialist Sarah Cobey, was recently published in Nature Medicine.
What evidence is there that lower dose vaccines may work against Covid-19? From full-scale clinical trials, it was found that the Oxford / AstraZeneca vaccine seemed to work best when the first injection consisted of a half-dose.
But there is a lot of data on the levels of antibodies that humans produce in response to even small doses. And according to a recent study published in Nature Medicine by David Khoury and colleagues, these antibodies are strongly linked to protection against Covid-19.
As Kremer and his colleagues note, if antibody levels are such that they provide good protection, then mRNA vaccines (BioNTech / Pfizer and Moderna) can protect just as highly effective AstraZeneca vaccines even if given in 2/3, 50 percent or even only 25 percent of the normal dose.
A recent preliminary report also found that a Moderna two-dose vaccine regimen, at 25 percent of the normal dose, produces an antibody response comparable to that of a Covid-19 sufferer.
A test is currently underway in Belgium to explore alternative doses of the Pfizer vaccine, and Moderna has said it is considering administering even lower doses. The concept of a standard or complete dose is more ambiguous than one might imagine.
These vaccines were developed very rapidly, and with a focus on effectiveness, which meant moving towards high doses. Melissa Moore, one of the chief scientific officers at Moderna, has acknowledged this. Therefore, it is likely that we will consider the current doses as very unnecessary.
This does not mean that we should abandon standard doses, which have been tried and tested in major clinical trials. But that we must immediately test the alternatives as well. But are there any weaknesses in this new scheme?
If lower-dose vaccines do not work as studies by antibodies suggest, this is a problem that booster doses may later adjust. Even more troubling is the prospect that a large group of people receiving low-dose vaccines may prompt the virus to evolve into vaccine resistance.
Cobey acknowledges this risk, but argues that if partial doses help reduce the number of infected people, it gives the virus less chance of undergoing mutations. Whether dangerous mutations can be reduced, rather than increased, is unclear.
But it is clear that millions of lives could be saved if partial dose vaccines are proven to work well. It’s the moment to learn a lesson. While the production and testing of these vaccines has been wonderful, next time we can do even better.
We need to conduct more testing and earlier in time to produce evidence on a wider variety of questions than “Are they safe?” and “Do they work?” Such tests are expensive; but it is enough to understand that what they give is worth paying for. / Translated by: Alket Goce-abcnews.al
