[{"command":"openDialog","selector":"#drupal-modal","settings":null,"data":"\u003Cdiv id=\u0022republish_modal_form\u0022\u003E\u003Cform class=\u0022modal-form-example-modal-form ecl-form\u0022 data-drupal-selector=\u0022modal-form-example-modal-form\u0022 action=\u0022\/en\/article\/modal\/7358\u0022 method=\u0022post\u0022 id=\u0022modal-form-example-modal-form\u0022 accept-charset=\u0022UTF-8\u0022\u003E\u003Cp\u003EHorizon articles can be republished for free under the Creative Commons Attribution 4.0 International (CC BY 4.0) licence.\u003C\/p\u003E\n \u003Cp\u003EYou must give appropriate credit. We ask you to do this by:\u003Cbr \/\u003E\n 1) Using the original journalist\u0027s byline\u003Cbr \/\u003E\n 2) Linking back to our original story\u003Cbr \/\u003E\n 3) Using the following text in the footer: This article was originally published in \u003Ca href=\u0027#\u0027\u003EHorizon, the EU Research and Innovation magazine\u003C\/a\u003E\u003C\/p\u003E\n \u003Cp\u003ESee our full republication guidelines \u003Ca href=\u0027\/horizon-magazine\/republish-our-stories\u0027\u003Ehere\u003C\/a\u003E\u003C\/p\u003E\n \u003Cp\u003EHTML for this article, including the attribution and page view counter, is below:\u003C\/p\u003E\u003Cdiv class=\u0022js-form-item form-item js-form-type-textarea form-item-body-content js-form-item-body-content ecl-form-group ecl-form-group--text-area form-no-label ecl-u-mv-m\u0022\u003E\n \n\u003Cdiv\u003E\n \u003Ctextarea data-drupal-selector=\u0022edit-body-content\u0022 aria-describedby=\u0022edit-body-content--description\u0022 id=\u0022edit-body-content\u0022 name=\u0022body_content\u0022 rows=\u00225\u0022 cols=\u002260\u0022 class=\u0022form-textarea ecl-text-area\u0022\u003E\u003Ch2\u003EFive things you need to know about: Delaying the gap between Covid-19 vaccine doses\u003C\/h2\u003E\u003Cp\u003EThe rationale is that, with the virus raging alongside uncertainty about vaccine supply, \u003Ca href=\u0022https:\/\/app.box.com\/s\/uwwn2dv4o2d0ena726gf4403f3p2acnu\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Evaccinating a greater number of people with a single dose\u003C\/a\u003E would be more effective at preventing deaths and hospitalisations than if a smaller number of people received two doses. However critics question the wisdom of moving away from the timetable tested during clinical trials.\u003C\/p\u003E\u003Cp\u003EHere are five things to know about the evidence and potential implications of delaying vaccine doses.\u003C\/p\u003E\u003Cp style=\u0022padding-left: 30px;\u0022\u003E\u003Cstrong\u003E1. There is little trial evidence to show what impact this will have on the Pfizer\/BioNTech vaccine\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EWhen UK officials announced the new guidelines, two vaccines had been authorised for use.\u003C\/p\u003E\u003Cp\u003EThe first vaccine \u2014\u0026nbsp;from Pfizer\/BioNTech and now being rolled out across Europe \u2014\u0026nbsp;uses \u003Ca href=\u0022https:\/\/horizon-magazine.eu\/article\/five-things-you-need-know-about-mrna-vaccines.html\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Enew technology\u003C\/a\u003E that introduces genetic material, called mRNA, which contains the instructions to make the so-called spike protein of the coronavirus into the body to elicit an immune response. Two weeks after the second dose, the vaccine showed a spectacular efficacy of 95%.\u003C\/p\u003E\u003Cp\u003ETrials for this vaccine did not test different dose gaps, nor did they evaluate the impact of one versus two doses. In a peer-reviewed study, the companies showed that the efficacy of the vaccine was \u003Ca href=\u0022https:\/\/pubmed.ncbi.nlm.nih.gov\/33301246\/\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003E52.4% between the first and second dose\u003C\/a\u003E \u2014\u0026nbsp;which were spaced 21 days apart.\u003C\/p\u003E\u003Cp\u003EHowever, UK officials suggested that in the trial most of the \u2018vaccine failures\u2019, where people got Covid-19 despite having been vaccinated, were in the period shortly after the first dose.\u0026nbsp;Between day 15 and 21, the observed efficacy against symptomatic Covid-19 was estimated at 89%, leading officials to conclude that\u003Ca href=\u0022https:\/\/app.box.com\/s\/uwwn2dv4o2d0ena726gf4403f3p2acnu\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003E \u2018short term protection from dose 1 is very high from day 14 after vaccination\u2019\u003C\/a\u003E.\u003C\/p\u003E\u003Cp\u003EBut scientists have underscored that the levels of so-called neutralising antibodies \u2014 which immunologists contend are the most formidable weapons of the immune arsenal \u2014 appear to increase \u003Ca href=\u0022https:\/\/www.immunology.org\/policy-and-public-affairs\/briefings-and-position-statements\/COVID-19-vaccine-dosing-schedules\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Edramatically only after the second dose\u003C\/a\u003E.\u003C\/p\u003E\u003Cp\u003EMeanwhile, the companies themselves issued a \u003Ca href=\u0022https:\/\/www.reuters.com\/article\/health-coronavirus-germany-biontech\/update-1-biontech-says-no-data-to-support-delayed-vaccine-booster-shot-idUSL1N2JF1GF\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Estatement\u003C\/a\u003E saying: \u2018There is no data to demonstrate that protection after the first dose is sustained after 21 days.\u2019\u003C\/p\u003E\u003Cp style=\u0022padding-left: 30px;\u0022\u003E\u003Cstrong\u003E2. There is some evidence that delaying the second dose of the Oxford\/AstraZeneca vaccine could be beneficial\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EThe second vaccine, made by Oxford\/AstraZeneca, is based on technology that has been successfully used before: a harmless chimp cold virus tweaked so that it carries genetic material containing the instructions for the spike protein.\u003C\/p\u003E\u003Cp\u003EClinical studies evaluating the Oxford-AstraZeneca vaccine did include spacing doses by two to three months, which appeared to trigger a stronger immune response. But the data was taken from a small subset of patients who received a half dose plus full dose, versus the majority of participants who received two standard doses a few weeks apart.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EData from the two standard doses showed an overall efficacy of 62%. But a dosing error that gave a subset of clinical trial participants half a dose followed by a full dose, actually shored up efficacy to 90%. The numbers in the subset of patients were met with cautious optimism \u2014 due to the small number of patients and because no patient was older than 55.\u003C\/p\u003E\u003Cp\u003EHowever, the UK healthcare regulator suggested that the greater efficacy of the half-dose\/full-dose regime was more likely down to a larger time interval between doses, rather than the regime. The agency conducted an exploratory analysis estimating efficacy against symptomatic Covid-19 of \u003Ca href=\u0022https:\/\/app.box.com\/s\/uwwn2dv4o2d0ena726gf4403f3p2acnu\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003E73% after the first dose\u003C\/a\u003E.\u003C\/p\u003E\u003Cp style=\u0022padding-left: 30px;\u0022\u003E\u003Cstrong\u003E3. Different vaccines may need different approaches\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EDr Mariola Fotin-Mleczek, chief technology officer of CureVac, \u003Ca href=\u0022https:\/\/horizon-magazine.eu\/article\/so-far-so-good-view-inside-coronavirus-vaccine-trial.html\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Ea German company in the late stages of developing its own Covid-19 mRNA vaccine\u003C\/a\u003E says she was sceptical of employing a one-size-fits-all approach for vaccines with different mechanisms of action.\u003C\/p\u003E\u003Cp\u003EFor mRNA vaccines like the CureVac candidate (and the Pfizer\/BioNTech product) the first dose primes the immune system but the immune response is not fully established, she says. \u2018Without boosting it in the next few weeks, the antibody responses go down further. Therefore, you need to test what the impact would be \u2026 on protection. Currently, data on whether protection will persist are missing,\u2019 she said.\u003C\/p\u003E\u003Cp\u003EThe World Health Organisation appears to agree with this analysis, suggesting that while there is some data to support delaying doses for the Oxford\/AstraZeneca vaccine there is no scientific evidence to \u003Ca href=\u0022https:\/\/www.theguardian.com\/world\/2021\/jan\/05\/no-data-to-support-uk-delay-of-vaccines-second-dose-says-who\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Estretch the second dose of the Pfizer\/BioNTech vaccine\u003C\/a\u003E to 12 weeks.\u003C\/p\u003E\u003Cp\u003E\u003Cblockquote class=\u0022tw-text-center tw-text-blue tw-font-bold tw-text-2xl lg:tw-w-1\/2 tw-border-2 tw-border-blue tw-p-12 tw-my-8 lg:tw-m-12 lg:tw--ml-16 tw-float-left\u0022\u003E\n \u003Cspan class=\u0022tw-text-5xl tw-rotate-180\u0022\u003E\u201c\u003C\/span\u003E\n \u003Cp class=\u0022tw-font-serif tw-italic\u0022\u003E\u2018Currently, data on whether protection will persist are missing.\u2019\u003C\/p\u003E\n \u003Cfooter\u003E\n \u003Ccite class=\u0022tw-not-italic tw-font-normal tw-text-sm tw-text-black\u0022\u003EDr Mariola Fotin-Mleczek, Chief Technology Officer, CureVac \u003C\/cite\u003E\n \u003C\/footer\u003E\n\u003C\/blockquote\u003E\n\u003C\/p\u003E\u003Cp style=\u0022padding-left: 30px;\u0022\u003E\u003Cstrong\u003E4. There are fears that weaker protection could accelerate vaccine-resistant mutations in the virus \u2013 but scientists are divided\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EAlthough it is not known how protective a single injection is over a longer term, it is also unclear how durable protection from two doses is. The effect of either vaccine to thwart viral transmission is also not conclusive.\u003C\/p\u003E\u003Cp\u003EHowever, scientists have \u003Ca href=\u0022https:\/\/www.theguardian.com\/commentisfree\/2021\/jan\/06\/mrna-vaccines-schedule-covid-19\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Eexpressed concerns\u003C\/a\u003E that a weak response to the virus in people who have received the first dose could accelerate the virus\u2019 ability to develop vaccine-resistant mutations.\u003C\/p\u003E\u003Cp\u003E\u2018My concern, as a virologist, is that if you wanted to make a vaccine-resistant strain, what you would do is to build a cohort of partially immunized individuals in the teeth of a highly prevalent viral infection,\u2019 Rockefeller University\u2019s Paul Bieniasz \u003Ca href=\u0022https:\/\/www.statnews.com\/2021\/01\/04\/britain-takes-a-gamble-with-covid-19-vaccines-upping-the-stakes-for-the-rest-of-us\/\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Etold \u003C\/a\u003ESTAT News.\u003C\/p\u003E\u003Cp\u003EOther scientists think the threat of that occurring is \u003Ca href=\u0022https:\/\/www.nature.com\/articles\/d41586-021-00045-8\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003Esmall\u003C\/a\u003E on the basis that the virus would struggle to undermine the complex antibody responses generated by vaccines.\u003C\/p\u003E\u003Cp style=\u0022padding-left: 30px;\u0022\u003E\u003Cstrong\u003E5. Delaying doses could undermine adherence to other vaccine schedules\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EAlthough it is understandable why governments would delay the second dose in an emergency situation, it\u0027s not great for the broader environment of building confidence in vaccines and science, says Professor Heidi Larson, the founding director of the Vaccine Confidence Project at the London School of Hygiene \u0026amp; Tropical Medicine, UK.\u003C\/p\u003E\u003Cp\u003EOne of the biggest concerns parents have about vaccines is around scheduling \u2014 they often wonder if it\u2019s possible to space out vaccinations due to the perception that their child\u2019s immune system might get overloaded, says Prof. Larson.\u003C\/p\u003E\u003Cp\u003EThe explanation they are given is that it\u2019s important to stick to the schedule because that\u2019s the way the vaccines are most effective, she notes, highlighting that this decision therefore breaks that confidence that scientists like her have been trying to foster in the scientific process.\u003C\/p\u003E\u003Cp\u003E\u2018It just gives the public a sense of they tell us one thing \u2026 and then they go off and do \u2014 what we\u0027ve been telling parents they can\u0027t do \u2014\u0026nbsp;which is change the schedule,\u2019 she said, adding that this decision has implications for vaccine confidence far beyond the current pandemic.\u003C\/p\u003E\u003Cp\u003E\u2018This is a hugely historic moment for many reasons,\u0026nbsp;and this will not be forgotten. So, don\u0027t just think about the emergency \u2026 think about the implications for confidence, and for rebuilding post Covid.\u2019\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003ECureVac, BioNTech and Prof. Larson have received funding from the EU. 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