COVID is skyrocketing in Seychelles, the most vaccinated country in the world. why?

Seychelles, a small archipelago country northeast of Madagascar in the Indian Ocean, has emerged as the most vaccinated country in the world for COVID-19.

Around 71% of people We have been vaccinated at least once with the COVID vaccine and 62% are fully vaccinated. these, 57% are vaccinated with Sinopharm vaccine, And 43 percent AstraZeneca.

Nevertheless, the number of cases has increased rapidly recently, with 37% of newly active cases and 20% of hospital cases. Fully vaccinated..The country had to do Imposing some restrictions..

How is this happening? There are several possible explanations:

1. 1.1.

   Herd immunity threshold not reached — 62% of vaccines may not be appropriate for the vaccine used

2. 2.2.

   Herd immunity cannot be reached due to the inadequate effectiveness of the two vaccines used.

3. 3.3.

   Mutants that escape vaccine protection predominate in Seychelles

4. 4.4.

   B.1.617 Indian variants are widespread and appear to be more infectious than other variants.

5. 5.5.

   The vaccine was disabled due to a major failure of cold chain logistics required for transportation and storage.

What does the national experience teach us about mutants, vaccine efficacy, and herd immunity? Let’s disassemble this.

Mutants can escape vaccine protection

There is Report Of the South African B.1.351 variant circulating in Seychelles. The virus has so far demonstrated its greatest ability to escape vaccine protection for all COVID mutants.

In South Africa, according to one study, AstraZeneca 0-10% effectiveness for this variantTo the South African government Stop using the vaccine During February.

The efficacy of the Sinopharm vaccine against this mutant is unknown, but laboratory studies Shows some reduction in protection based on a blood test, But maybe some protection.

However, there is no comprehensive surveillance in the country to determine the proportion of cases caused by South African variants.

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The British subspecies B.1.1.7, which is more contagious than the original strain, has become the predominant subspecies in the United States.But the United States is still Achieved a dramatic reduction in COVID-19 Most people are vaccinated against Pfizer and Modana.

Israel, which was dominated by British variants, also has a very high vaccination rate, with nearly 60% of the population vaccinated with Pfizer.I got you 92% effectiveness For all infectious diseases, including asymptomatic infections, and Israel Significant reduction in new cases..

In the UK, we use a combination of Pfizer vaccine and AstraZeneca vaccine. Over 50 percent of the population It is given as a single dose and almost 30 percent are fully vaccinated. The country has also seen a significant reduction in the number of cases.

But there is now Increasing number of cases in northwest EnglandMost new cases in the city of Bolton are Indian variants.This variant is also the cause Outbreak in SingaporePreviously, I had good control over the virus.

Seychelles needs to perform urgent genomic sequencing and surveillance to see what contributions of the variant of concern are and whether Indian variants exist.

If the South African variant is predominant, the country needs to use a vaccine that works well against it. Many companies make boosters targeting this variant, but for now, Pfizer is an option.In Qatar, local researchers discovered what Pfizer had 75% efficacy against South African variants..

Highly efficient vaccines must be used to achieve herd immunity

The· Reported effectiveness 79% of China National Pharmaceutical, AstraZeneca 62-70% of phase 3 clinical trials..

Our study at The Kirby Institute has shown that in New South Wales, the use of a vaccine that is 90% effective against all infections means that herd immunity can be achieved. If 66 percent of the population is vaccinated..

However, with less effective vaccines, more people need to be vaccinated. If the vaccine is 60% effective, the percentage of people who need vaccination will increase to 100%.

Herd immunity cannot be achieved if the efficacy is less than 60%.

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However, these calculations were made for normal COVID-19 caused by the D614G variant. Dominate in 2020.. The reproduction number (R0) of this is 2.5. In other words, an average of 2.5 people infected with the virus will be infected.

But the B.1.1.7 variant More contagious than 43-90 percent Larger than D614G, R0 can be up to 4.75. This requires higher vaccination rates to control spread.

In addition, the Indian subspecies B.1.617 is at least 50% more contagious than B.1.1.7, This could make R0 7 or higher and takes us to an unknown territory.

This may explain the catastrophic situation in India, but it also increases the risk of vaccination because less effective vaccines cannot effectively contain such highly contagious mutants. ..

Herd immunity is still possible, It depends on the effectiveness of the vaccine used and the percentage of people who will be vaccinated...

A British modeling studies found With very ineffective vaccines, infections cannot be controlled and the economy will hardly collapse after more than a decade. On the other hand, the use of highly effective vaccines has far better economic outcomes.

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Immunizing the world is the only way to end a pandemic

As pandemics continue to worsen in some parts of the world, the risk of more dangerous mutations that are too resistant or contagious to be controlled by current vaccines increases.

Keeping up with mutations is like whac-a-mole while the pandemic is rampant.

The take-out message of our pandemic exit strategy is that the sooner we vaccinate the world, the faster we will control the emergence of new variants.

Raina MacIntyre is a professor of global biosecurity at NHMRC. Principal Investigator at UNSW’s Kirby Institute and Head of Biosecurity Program.This work first appeared conversationn.