Vaccine skeptics pronounced themselves vindicated, while international health experts have been scrambling to answer a host of questions without the benefit of robust data. Did\u00a0one or both of the vaccines<\/a>\u00a0used in Seychelles fail? Has herd immunity not been reached? Is the nation grappling with a more infectious variant capable of evading the defenses that certain types of vaccines provide?<\/p>\n \u201cSo what\u2019s going on?\u201d asked Raina MacIntyre, professor of global biosecurity at the Sydney campus of the University of New South Wales, during an online presentation on May 18. \u201cIt\u2019s probably that the herd immunity threshold hasn\u2019t been reached, plus or minus, if it\u2019s the South African variant in there.\u201d<\/p>\n The answers to the questions MacIntyre and other experts are posing may influence the future course of the pandemic. For starters, the tiny nation has become a test case for two of the world\u2019s most widely used vaccines. In the Seychelles, 57% of the vaccinated population received Sinopharm\u2019s shot, and 43% got the Covishield vaccine developed by AstraZeneca Plc. Sinopharm\u2019s inoculation has been donated or sold to countries around the globe, including Indonesia, Venezuela, and Zimbabwe; Covishield makes up the bulk of shots distributed to poor nations in Africa and elsewhere through the\u00a0Covax initiative<\/a>, which seeks to make vaccine distribution more equitable.<\/p>\n What\u2019s happening in Seychelles is very different from the experience of Israel, the second-most vaccinated nation, where Covid-19 infections have plummeted. The contrast could yield crucial insights into the efficacy of the different types of immunizations. In Israel the\u00a0dominant vaccine<\/a>\u00a0was the messenger ribonucleic acid shot made by Pfizer Inc. and BioNTech SE.<\/p>\n The pandemic has seen mRNA vaccines\u2014 Moderna Inc. makes another\u2014being used in scale for the first time. Data from clinical trials so far suggest they are better at stopping Covid, tackling variants, and preventing the virus from spreading in the community. Sinopharm\u2019s and AstraZeneca\u2019s vaccines rely on more traditional methods, and their shots have been shown to have lower efficacy in studies.<\/p>\n What\u2019s also apparent, so far, is that though there\u2019s been a surge in cases in Seychelles, very few people are getting seriously ill. \u201cWe have only a few people needing intensive care. Two out of 40\u201d in hospitals, said Seychelles President Wavel Ramkalawan in a May 10 interview. \u201cThe vaccine will protect people from getting serious symptoms.\u201d<\/p>\n Still, more answers are needed. The government hasn\u2019t disclosed what vaccine was administered in the breakthrough cases that make up a third of the total count. No agency has done any genomic sequencing to determine which variant is dominant on the islands, though the one first identified in South Africa, B.1.351, was detected in Seychelles in February.<\/p>\n On May 13, Jude Gedeon, the country\u2019s public-health commissioner, said samples were to be sent to the Kenya Medical Research Institute for testing. The World Health Organization is also taking action. \u201cWe are very concerned, and we are sending a multidisciplinary team there to help the Seychelles government address the situation,\u201d says Richard Mihigo, program area manager for immunization and vaccine development at the WHO\u2019s regional office for Africa in Brazzaville, Republic of Congo. \u201cWe are also in discussion with the government to conduct a vaccine effectiveness study.\u201d<\/p>\n The situation in Seychelles also offers a fresh reminder that our understanding of herd immunity\u2014the theoretical threshold at which the virus can\u2019t find enough hosts to keep spreading\u2014continues to evolve. Scientists once estimated that 55% to 82% of the population would need to have immunity against SARS-CoV-2, either from recovering from an infection or through vaccination. But 17 months into the pandemic, there\u2019s recognition that the threshold may vary depending on the susceptibility of a population to the circulating strains, adherence to physical distancing, mask-wearing, and other practices known to reduce transmission, as well as the season\u2014epidemics typically worsen as either colder or hotter weather encourages people to congregate indoors.<\/p>\n \u201cIt\u2019s probably not likely that we are going to drive to zero the transmission of this virus or have it disappear,\u201d says Jennifer Nuzzo, an epidemiologist and senior scholar at the Johns Hopkins Center for Health Security in Baltimore. Still, she see vaccines \u201cdoing the thing that we care most about, which is preventing serious illness.\u201d<\/p>\n Lessons from Seychelles could be valuable to other countries in assembling their own vaccine arsenals, through purchases or donations\u2014or a combination of the two, as the tropical nation did. \u201cIt\u2019s about quality vaccines that are shown to be effective against your variant,\u201d says Glenda Gray, president of the South African Medical Research Council and co-lead of a Johnson & Johnson Covid vaccine trial in the country.<\/p>\n Finance Minister Naadir Hassan, who had to steer Seychelles\u2019s economy through a 13% contraction in 2020, says the government cannot afford to stand still while it awaits answers to these Covid riddles. The country is \u201can open, vulnerable economy,\u201d he said in a May 13 interview. \u201cThe country needs to be safe, and the country needs to be open.\u201d<\/p>\n More stories like this are available on\u00a0bloomberg.com<\/a><\/p>\n \u00a92021 Bloomberg L.P.<\/p>\n![\"chart,](\"{"default":{"load":"default","w":"80","h":"36","src":"\/\/img-s-msn-com.akamaized.net\/tenant\/amp\/entityid\/AAKqxBE.img?h=363&w=799&m=6&q=60&o=f&l=f"},"size3column":{"load":"default","w":"62","h":"28","src":"\/\/img-s-msn-com.akamaized.net\/tenant\/amp\/entityid\/AAKqxBE.img?h=284&w=624&m=6&q=60&o=f&l=f"},"size2column":{"load":"default","w":"62","h":"28","src":"\/\/img-s-msn-com.akamaized.net\/tenant\/amp\/entityid\/AAKqxBE.img?h=284&w=624&m=6&q=60&o=f&l=f"}}\")