By Victor Argonov, senior analyst at EXANTE
An increasing number of studies shows that the new South African strain of COVID can infect people who have already had the disease, and that vaccines have little effect on it. It is possible that the entire current vaccination program could be rendered ineffective by this strain, that the vaccines will have to be improved, and the vaccination will have to be restarted from scratch. However, is the panic really justified?
If we disregard the immediate emotional reaction and consider the statistics that we currently have, we can realize that the mass vaccination is still capable of stopping the South African strain, just like all the others. Its basic reproduction number, or R0, is 50% higher than that of the more common strain. In other words, every person infected with the new strain infects 1.5 times as many people as the person infected with the old strain. If the measures taken against the spread of the disease can keep the effective reproduction number, or R, at, say, 0.9 (which means that the number of new cases is decreasing), the new strain will increase that number to 1.35 (meaning that the number of new cases is increasing). Regardless, the current vaccines can keep R below 1 for all strains. Let us prove this.
Here is how effective the current vaccines are against the South African strain.
- BioNTech claims that the vaccine it has developed together with Pfizer is almost as effective against the South African strain as it is against the other strains. However, this conclusion was made based on the blood plasma samples taken from just 20 infected people.
- The Novavax vaccine, which is to be deployed soon, is 96% effective against the common strain, 86% effective against the British strain, but only 49% effective against the South African strain.
- The Johnson & Johnson vaccine, which is currently undergoing the third phase of testing, is 72% effective against the common strain, and 57% effective against the South African strain.
Even if we take the worst percentage, Novavax’s 49%, as the baseline, vaccinating 100% of the population will halve R. If it was at 1.35 before the vaccination, it will drop to 0.75 afterward. Even if we vaccinate 2/3 of the population, which is a much more realistic estimate, R will decrease by about 1/3 to 0.9. If we also take into account that a significant part of the population in affected countries has already had the disease (and therefore immune to some degree), then vaccinating half of the population may already be sufficient.
And these are the numbers for the Novavax vaccine. The Johnson & Johnson vaccine is going to fare even better against the new strain, while the makers of the Pfizer-BioNTech vaccine don’t see much of a problem with the new strain at all.
By the way, Israel currently has the highest vaccination rate in the world, having vaccinated 54% of the country’s population. If the calculations above are correct, Israel has almost achieved complete victory against COVID, and the new South African strain can do little to change that.