Two Pfizer Covid vaccine doses give over 95% protection, shows Israel study | Coronavirus
Two doses of the Pfizer/BioNTech vaccine have proved more than 95% effective against infection, hospitalisation and death from Covid-19 in Israel, the country with the highest proportion of its population vaccinated in the world, research has found.
One shot of the vaccine was partially effective, offering 58% protection against infection, 76% against hospitalisation, and 77% against death. The authors of the observational study in the Lancet medical journal say this shows the importance of having the second shot.
Their study demonstrates the power of vaccines to end the toll of coronavirus, they say. “These findings suggest that high vaccine uptake can meaningfully stem the pandemic and offers hope for eventual control of the Sars-CoV-2 outbreak as vaccination programmes ramp up across the rest of the world,” they wrote.
Lead author, Dr Sharon Alroy-Preis, of the Israel ministry of health, said: “Until this point, no country in the world had described the national public health impact of a nationwide Covid-19 vaccination campaign. These insights are hugely important because, while there are still some considerable challenges to overcome, they offer real hope that Covid-19 vaccination will eventually enable us to control the pandemic.”
But many other countries will not be able to imitate Israel, commentators in the journal say.
“Regrettably, rapid population-level coverage cannot be easily replicated in many other countries. The global use of the [Pfizer/BioNTech] vaccine is limited by supply issues, high costs, and ultra-cold chain storage requirements,” wrote Prof Eyal Leshem of the Chaim Sheba Medical Centre in Israel, and Prof Annelies Wilder-Smith of the London School of Hygiene & Tropical Medicine, who were not involved in the study.
Israel has used only the Pfizer/BioNTech vaccine, which the company supplied on the understanding that data from the vaccination programme would be published to demonstrate its real-world efficacy.
The country had a national lockdown from 27 December 2020 until 7 March 2021 because of a big surge in infections, which peaked in January. By 3 April, 72% of adults over 16 and 90% of the over-65s had received two doses of the vaccine. As in the UK, the dominant strain of the virus has been the “Kent” variant, B117. Some cases of the “South African” variant, B1351, have been found latterly, but too few to be taken into account.
By seven days after the second dose, the vaccine was giving people 95.3% protection against infection and 96∙7% protection against death. Protection against symptomatic and asymptomatic infection was 97.0% and 91.5%, respectively. Protection against hospital admission was 97.2% overall. By 14 days after the second dose, the protection had risen slightly further.
The authors, some of whom declared shares in Pfizer, wrote that “relying on protection against Covid-19 from a single dose might not be prudent”. The vaccine was developed to be given as two shots and substantially higher levels of antibodies have been observed after the second dose.
“Additionally, little is known about the duration of protection of one dose and how it compares with the durability after two doses. It is possible that one dose will provide a shorter duration of protection than two doses, particularly in an environment where new Sars-CoV-2 variants continue to emerge,” they wrote.
In a separate study published in the BMJ on Thursday, researchers from Denmark and Norway revealed their investigations into the blood clots that have been linked to the Oxford/AstraZeneca vaccine. They looked at 280,000 people aged 18-65 who received a first dose of the vaccine in the two countries in February and March.
They found more clots in the veins than would be expected, although the events were still rare – 11 per 100,000 vaccinations. There were 2.5 clots in the veins of the brain per 100,000 jabs.
In a linked opinion, Prof Paul Hunter at the University of East Anglia, said the study did not change the conclusions of the UK and European medicine regulators that the benefits of the Oxford/AstraZeneca vaccine far outweigh its risks for most age groups.
“Those countries that delayed their own vaccination programmes at a time of high transmission rates by declining to use available Oxford/AstraZeneca vaccines should know that their decision will have contributed to an increase in the number of avoidable deaths from Covid-19,” he writes.
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