The Seychelles archipelago, northeast of Madagascar in the Indian Ocean, is the country with the highest number of vaccinated people in the world. About 71% of people have received at least one dose of a COVID vaccine, and 62% have been fully vaccinated.
Of these, 57% received the Sinopharm vaccine and 43% AstraZeneca. But despite this, the country has recorded an increase in cases, with 37% of new active cases and 20% of hospitalized cases being fully vaccinated.
The country has restored restrictions.
But what are the reasons?
-the herd immunity has not yet been achieved
Herd immunity may be impossible due to inadequate efficacy of the two vaccines used
-vaccines that escape vaccine protection are dominant in the Seychelles
-Indian variant B1617 is spreading rapidly, which is even more contagious than other variants
-massive logistics failures required for the transport and storage of vaccines may have affected the ineffectiveness of vaccines.
What does the country’s experience tell us about variants, vaccine efficacy, and herd immunity?
Variants can escape vaccine protection
There are reports of the South African variant B.1.351 circulating in the Seychelles. This variant has been shown to escape vaccine protection of all COVID variants to date.
According to a study AstraZeneca has 0-10% efficacy against the African variant, prompting the South African government to ban the use of the vaccine in February. The effectiveness of the Sinopharm vaccine against this variant is not yet known, but laboratory studies show that the vaccine does not provide much protection, based on blood tests.
The British variant B117, which is more sticky than the original type, is the dominant variant in the United States. But the US managed to control COVID-19 through vaccination, with most people receiving the Pfizer and Moderna vaccines, reports abcnews.al
Israel, where the British variant was more dominant, also has a very high vaccination rate, having vaccinated nearly 60% of its population with Pfizer.
Pfizer has 92% effectiveness against any infection including asymptomatic cases and Israel has seen a decrease in new cases. The UK has used a combination of Pfizer and AstraZeneca vaccines. More than 50% of the population have received a single dose and almost 30% have been fully vaccinated. The country has also seen a decline in the number of new cases.
But there is a current increase in cases in North West England, with most of the new cases in the town of Bolton being the Indian variant. This variant has also spread massively in Singapore, which has managed to keep Covid-19 in control.
Seychelles must conduct urgent genome sorting to see which variant has contributed to the proliferation of new cases. If the African variant is predominant, the country should use a vaccine that works well against it.
For now, Pfizer would be an option. In Qatar, local researchers found that Pfizer was 75% effective against the South African variant, reports abcnews.al
We need to use high-efficiency vaccines to achieve herd immunity
The effectiveness of Sinopharm is 79% and AstraZeneca 62-70%, based on phase-to-phase clinical trials. According to research at the Kirby Institute in New South Wales, Australia, using a vaccine with 90% efficacy means that herd immunity can be achieved if 66% of the population is vaccinated.
However, the use of vaccines with lower efficacy means that the rate of vaccination should be increased. If the vaccine is 60% effective, the percentage of the population to be vaccinated should be 100%.
If 60% of the population is vaccinated, herd immunity will not be possible.
However, these data were collected during 2020 where the dominant variant was D614G. This has a reproductive number (R0) of 2.5, which means that people infected with the virus infect an average of 2.5 others.
But the B117 variant is 43-90% more sticky than the D614G, so R0 could be up to 4.75. This will require higher vaccination rates to control the spread. Moreover, the Indian variant B1617 is estimated to be at least 50% more sticky than the B117, which could increase R0 to over 7, reports abcnews.al
This may explain the catastrophic situation in India, but also increases the risks for vaccination, as lower efficacy vaccines will not be able to control such variants.
Herd immunity has not yet been achieved, but it depends on the effectiveness of the vaccine and the percentage of people vaccinated. A UK modeling study found that using vaccines with very low efficacy would result in the biggest economic downturn for another 10 years.
Vaccination of the whole world is the only way to end the pandemic
As the pandemic continues to spread in some parts of the world, the risk of mutations that are resistant to vaccines also increases. The only way to end the pandemic is to vaccinate the entire population. abcnews.al