Cautious optimism over Oxford-AstraZeneca candidate vaccine results

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The candidate coronavirus vaccine AZD1222,  being developed by University of Oxford and AstraZeneca, generated an immune response in a study of roughly 1,000 patients, according to interim results published Monday. The results show a relatively safe vaccine – though side effects were greater than for a meningitis vaccine – and future studies will likely test giving patients two doses.

Medical Xpress reports that the early stage trial finds that the vaccine is safe, causes few side effects, and induces strong immune responses in both parts of the immune system – provoking a T cell response within 14 days of vaccination (a cellular immune response, it could find and attack cells infected with the virus), and an antibody response with 28 days (humoral immune response, it could find and attack the virus when it was circulating in the blood or lymphatic system).

An ideal vaccine against SARS-CoV-2 should be effective after one or two vaccinations, work in target populations including older adults and those with other health conditions, confer protection for a minimum of six months, and reduce onward transmission of the virus to contacts. The current trial is too preliminary to confirm whether the new vaccine meets these requirements, but phase 2 (in the UK only) and phase 3 trials to confirm whether it effectively protects against SARS-CoV-2 infection are happening in the UK, Brazil and South Africa.

Explaining how the vaccine works, study lead author Professor Andrew Pollard, University of Oxford, UK, says: "The new vaccine is a chimpanzee adenovirus viral vector (ChAdOx1) vaccine that expresses the SARS-CoV-2 spike protein. It uses a common cold virus (adenovirus) that infects chimpanzees, which has been weakened so that it can't cause any disease in humans, and is genetically modified to code for the spike protein of the human SARS-CoV-2 virus. This means that when the adenovirus enters vaccinated people's cells it also delivers the spike protein genetic code. This causes these people's cells to produce the spike protein, and helps teach the immune system to recognise the SARS-CoV-2 virus."

He continues: "The immune system has two ways of finding and attacking pathogens—antibody and T cell responses. This vaccine is intended to induce both, so it can attack the virus when it's circulating in the body, as well as attacking infected cells. We hope this means the immune system will remember the virus, so that our vaccine will protect people for an extended period. However, we need more research before we can confirm the vaccine effectively protects against SARS-CoV-2 infection, and for how long any protection lasts."

The new trial included 1,077 healthy adults aged 18-55 years with no history of COVID-19, and took place in five UK hospitals between 23 April and 21 May 2020. The data included in the paper covered the first 56 days of the trial and is ongoing. The participants either received the new COVID-19 vaccine (543 people) or the meningococcal conjugate vaccine (534 people). 113 participants (56 given the COVID vaccine, and 57 in the control group) were also asked to take paracetamol before and for 24 hours after their vaccination to help reduce vaccine-associated reactions (as the COVID-19 vaccine was given in a high dose to help induce a strong immune response).

All participants gave additional blood samples and underwent clinical assessments to determine if the vaccine was safe and whether it provoked an immune response. Participants were also asked to record any adverse events throughout the trial.

The participants were split into four groups. Group 1 (88 people) had additional safety monitoring to form the phase 1 part of the trial, and had antibody and T cell responses assessed. Group 2 (412 people) had extra blood taken to assess for antibody and T cell responses, and group 4 (567 people) had serum taken to assess for antibody response only. In groups 1, 2 and 4 half the participants received the COVID-19 vaccine and half received the control vaccine. Group 3 (10 people) received only the COVID-19 vaccine, and were given an extra dose of vaccine 28 days after the first dose to determine safety and whether this boosted antibody and T cell responses.

The vaccine was found to have an acceptable safety profile and there were no serious adverse events. Fatigue and headache were the most commonly reported reactions (around 70% [340/487] of all participants given the COVID-19 vaccine only reported fatigue, and 68% [331/487] reported headache, compared with around 48% [227/477] and 41% [195/477], respectively, of participants in the control group without paracetamol). Other common side effects included pain at the injection site, muscle ache, malaise, chills, feeling feverish, and high temperature.

Participants taking paracetamol around their vaccination had reduced pain, chills, feeling feverish, muscle ache, headache, and malaise in the two days following vaccination. In addition, in the 10 people who received the extra dose of the COVID-19 vaccine, side effects were less common after the second dose.

The authors found that there were strong antibody and T cell responses from the vaccine. T cell responses targeting the SARS-CoV-2 spike protein were markedly increased (in the 43 participants studied), peaking 14 days after vaccination (median 856 spot-forming cells per million peripheral blood mononuclear cells), with this level declining slightly by day 56 of the trial (to median 424 spot-forming cells per million peripheral blood mononuclear cells) . The T cell response did not increase with a second dose of the vaccine, which is consistent with other vaccines of this kind.

Antibody responses peaked by day 28 (median 157 ELISA units—studied in 127 participants) and remained high until the measurement at day 56 in the trial (median 119 ELISA units—studied in 43 participants) for those given a single vaccine. This response was boosted by a second dose (median 639 ELISA units at day 56 in these 10 participants).

28 days after vaccination, neutralising antibody responses against SARS-CoV-2 were detected in 32 of 35 participants (91%) (when measured in MNA80 neutralisation assay), and in 35 of 35 participants (100% – when measured in PRNT50 neutralisation assay) who received a single dose of the COVID-19 vaccine. These responses were present in all participants who had a booster dose of the vaccine (nine of nine participants in MNA80 assay at day 42, and ten of ten in Marburg VN assay on day 56).

The authors found that taking paracetamol did not affect immunogenicity of the COVID-19 vaccine.

Co-author, Professor Sarah Gilbert, University of Oxford, UK, says: "There is still much work to be done before we can confirm if our vaccine will help manage the COVID-19 pandemic, but these early results hold promise. As well as continuing to test our vaccine in phase 3 trials, we need to learn more about the virus – for example, we still do not know how strong an immune response we need to provoke to effectively protect against SARS-CoV-2 infection. If our vaccine is effective, it is a promising option as these types of vaccine can be manufactured at large scale. A successful vaccine against SARS-CoV-2 could be used to prevent infection, disease and death in the whole population, with high risk populations such as hospital workers and older adults prioritised to receive vaccination."

The authors note some limitations, including that more research is needed to confirm their findings in different groups of people – including older age groups, those with other health conditions, and in ethnically and geographically diverse populations. The authors note that these groups are being recruited in their ongoing phase 2 and 3 trials of the vaccine in the UK, Brazil and South Africa. In the current trial, 91% (979/1,077) of participants were white and the average age of participants was 35 years.

They also note that a small number of participants had detectable neutralising antibodies and T cell responses against SARS-CoV-2 spike protein before vaccination, likely to be due to past asymptomatic infection as potential participants with recent COVID-19-like symptoms or with a history of positive PCR test for SARS-CoV-2 were excluded from the study.

The authors say the participants recruited in this study will be followed-up for at least one year to continue to study the vaccine's safety and the immune response it provokes.

Writing in a linked comment discussing both articles, lead author assistant professor Naor Bar-Zeev (who was not involved in the two studies), International Vaccine Access Centre, Johns Hopkins Bloomberg School of Public Health, says: "These trial reports are hugely anticipated. The results of both studies augur well for phase 3 trials, where the vaccines must be tested on much larger populations of participants to assess their efficacy and safety… Both trials used adenovirus vectors to deliver and study the COVID-19 vaccine, an innovative and efficient means of vaccine development in the midst of a pandemic. Capable of generating humoral, cellular, and innate responses, adenovirus vectored vaccines have much potential."

However, he warns of the preliminary nature of the two vaccine candidates. He continues: "The platform [adenovirus vectored vaccines] only achieved European Commission regulatory licensure on July 1, 2020, with the Ebola vaccine. Much remains unknown about these and other COVID-19 vaccines in development, including longevity of response and immunogenicity in older adults or other specific groups, such as those with comorbidities who are often excluded from clinical trials, or ethnic or racial groups more severely affected by COVID-19."


STAT News reports that while the Oxford-AstraZeneca vaccine, known as AZD1222, has moved most rapidly into larger-scale studies of any major contender – and AstraZeneca has said that billions of doses could be manufactured – the new data represent the first glimpse researchers have gotten at its efficacy. They show a relatively safe vaccine – though side effects were greater than for a meningitis vaccine, to which it was compared – that engages the immune system to fight the virus. AstraZeneca said that, because of the results, it is likely that future studies will test giving patients two doses of the vaccine.

“At the end of the day, you have to prioritise efficacy and then resolve the challenges around the logistics of the trial or logistics of manufacturing large quantities of vaccine,” said Pascal Soriot, AstraZeneca’s CEO, in a briefing with reporters.

The report says The Lancet also published results of another vaccine, from the Chinese biotech CanSino, that had been previously released. The Phase 2 results showed that, as was seen in the Phase 1 data, the vaccine induced neutralizing antibody responses – which could be vital to preventing the disease’s dangerous symptoms – in most subjects. But further study continues to show that this vaccine works better in some people than others. And among those it didn’t work as well in were people aged 55 and older, a key target for COVID-19 vaccination.

“The results of both studies augur well for phase 3 trials, where the vaccines must be tested on much larger populations of participants to assess their efficacy and safety,” wrote Naor Bar-Zeev and William Moss, in the editorial.

Added Michael Ryan, the World Health Organisation’s health emergencies chief: “We now need to move into larger scale, real-world trials, but it is good to see more data, more products moving in to this very important phase of vaccine discovery.”

STAT News says the data on the Oxford-AstraZeneca vaccine do not provide enough information to predict whether it will be more effective than other vaccines that are also entering clinical trials.

AZD1222 is one of 23 potential COVID-19 vaccines that are being tested in clinical trials, according to the WHO. Studies in which thousands of volunteers are given either a vaccine or placebo are necessary to know for sure if any vaccine prevents infection with SARS-Cov-2, and how well that vaccine works. No such studies have been completed.

The report says in a paper also released Monday, BioNTech and Pfizer said their vaccine also induced T-cell responses.

But Mene Pangalos, an AstraZeneca executive vice president, warned during the company’s briefing that it is “almost impossible” to compare antibody levels between different vaccines because of variation in the tests used to measure them. He pointed out that AZD1222 has another advantage: it needs to be kept cold, but not frozen, as the messenger RNA vaccines do.

AZD1222, which was developed by researchers at Oxford’s Jenner Institute, works differently, by using a genetically engineered virus, called adenovirus, which was taken from chimps and modified not to replicate and sicken people. It carries a gene for one of the proteins in SARS-Cov-2 and inserts it into a recipient’s cells. The virus causes the patient’s cells to make that protein, which is then recognized by the immune system as foreign. This results in an immune response.

The report says the platform has not been used in an approved vaccine. But it has been used in experimental vaccines against the viruses that cause other outbreaks, including the Ebola virus and the virus that causes Middle East respiratory syndrome (MERS). That work left the Oxford group ready when SARS-CoV-2, a related virus, became a threat. Gilbert, who has been a key figure in developing the platform, known as ChAdOx1, said the data, though early, showed promise. “If our vaccine is effective, it is a promising option as these types of vaccine can be manufactured at large scale,” Gilbert said.

The report says CanSino, for its part, is now planning for a Phase 3 trial. Its vaccine is what’s known as a viral vector vaccine; it uses a live but weakened human cold virus, adenovirus 5 – known as Ad5 for short – as a delivery system that teaches the immune system to recognise the SARS-CoV-2 coronavirus.

Many people have had previous infections with adenovirus 5, raising concerns that the immune system would focus on the Ad5 parts of the vaccine rather than the SARS-Cov-2 material fused to it. Many research groups that work on viral-vectored vaccines stopped using Ad5 because of concerns about pre-existing immunity, which can run to 70% or higher in some populations.

The data released Monday showed subjects in the Phase 2 trial who had no or low-level pre-existing immunity to Ad5 developed neutralising antibodies to SARS-CoV-2 at roughly double the rate of people who had high-level pre-existing immunity. High-level pre-existing immunity was more common in people in the study aged 55 and older. The researchers said the vaccine’s response in older adults will be studied in a Phase 2b trial.

The report says the findings concern some experts.

Gary Kobinger, director of the Infectious Disease Research Centre at Laval University, Quebec, questioned whether it makes sense to pursue development of the vaccine, given the problem with pre-existing immunity to the Ad5 vector, and the relatively high rate of adverse events seen in the study. Most of the grade 3 reactions – the most severe – were seen in people who received the highest of two doses used in the study, though there was one report of a grade 3 fever in a person who received the lower dose. CanSino has dropped the higher dose.

But Kathryn Edwards, scientific director of the Vanderbilt Vaccine Research Programne in Nashville, noted the world is going to need as many COVID-19 vaccines as can be made. The CanSino vaccine may not be protective enough for older adults, she said, but it might be useful in children. To date the vaccine has only been studied in people 18 years and older.

The CanSino researchers suggested the dampening of the immune response due to pre-existing immunity to the Ad5 vector might be overridden by using a booster dose sometime between three and six months after the original dose – a potentially awkward dosing regimen that would not deliver rapid protection in the people who are at highest risk from COVID-19, older adults. Edwards said, though, that another dose might simply boost the immune response to the Ad5 vector, not the intended target, SARS-CoV-2.

The CanSino vaccine has already received an emergency license in China for use in the military.

Background: The pandemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) might be curtailed by vaccination. We assessed the safety, reactogenicity, and immunogenicity of a viral vectored coronavirus vaccine that expresses the spike protein of SARS-CoV-2.
Methods: We did a phase 1/2, single-blind, randomised controlled trial in five trial sites in the UK of a chimpanzee adenovirus-vectored vaccine (ChAdOx1 nCoV-19) expressing the SARS-CoV-2 spike protein compared with a meningococcal conjugate vaccine (MenACWY) as control. Healthy adults aged 18–55 years with no history of laboratory confirmed SARS-CoV-2 infection or of COVID-19-like symptoms were randomly assigned (1:1) to receive ChAdOx1 nCoV-19 at a dose of 5 × 1010 viral particles or MenACWY as a single intramuscular injection. A protocol amendment in two of the five sites allowed prophylactic paracetamol to be administered before vaccination. Ten participants assigned to a non-randomised, unblinded ChAdOx1 nCoV-19 prime-boost group received a two-dose schedule, with the booster vaccine administered 28 days after the first dose. Humoral responses at baseline and following vaccination were assessed using a standardised total IgG ELISA against trimeric SARS-CoV-2 spike protein, a muliplexed immunoassay, three live SARS-CoV-2 neutralisation assays (a 50% plaque reduction neutralisation assay [PRNT50]; a microneutralisation assay [MNA50, MNA80, and MNA90]; and Marburg VN), and a pseudovirus neutralisation assay. Cellular responses were assessed using an ex-vivo interferon-γ enzyme-linked immunospot assay. The co-primary outcomes are to assess efficacy, as measured by cases of symptomatic virologically confirmed COVID-19, and safety, as measured by the occurrence of serious adverse events. Analyses were done by group allocation in participants who received the vaccine. Safety was assessed over 28 days after vaccination. Here, we report the preliminary findings on safety, reactogenicity, and cellular and humoral immune responses. The study is ongoing, and was registered at ISRCTN, 15281137, and, NCT04324606.
Findings: Between April 23 and May 21, 2020, 1077 participants were enrolled and assigned to receive either ChAdOx1 nCoV-19 (n=543) or MenACWY (n=534), ten of whom were enrolled in the non-randomised ChAdOx1 nCoV-19 prime-boost group. Local and systemic reactions were more common in the ChAdOx1 nCoV-19 group and many were reduced by use of prophylactic paracetamol, including pain, feeling feverish, chills, muscle ache, headache, and malaise (all p<0·05). There were no serious adverse events related to ChAdOx1 nCoV-19. In the ChAdOx1 nCoV-19 group, spike-specific T-cell responses peaked on day 14 (median 856 spot-forming cells per million peripheral blood mononuclear cells, IQR 493–1802; n=43). Anti-spike IgG responses rose by day 28 (median 157 ELISA units [EU], 96–317; n=127), and were boosted following a second dose (639 EU, 360–792; n=10). Neutralising antibody responses against SARS-CoV-2 were detected in 32 (91%) of 35 participants after a single dose when measured in MNA80 and in 35 (100%) participants when measured in PRNT50. After a booster dose, all participants had neutralising activity (nine of nine in MNA80 at day 42 and ten of ten in Marburg VN on day 56). Neutralising antibody responses correlated strongly with antibody levels measured by ELISA (R2=0·67 by Marburg VN; p<0·001).
Interpretation: ChAdOx1 nCoV-19 showed an acceptable safety profile, and homologous boosting increased antibody responses. These results, together with the induction of both humoral and cellular immune responses, support large-scale evaluation of this candidate vaccine in an ongoing phase 3 programme.
Funding: UK Research and Innovation, Coalition for Epidemic Preparedness Innovations, National Institute for Health Research (NIHR), NIHR Oxford Biomedical Research Centre, Thames Valley and South Midland's NIHR Clinical Research Network, and the German Center for Infection Research (DZIF), Partner site Gießen-Marburg-Langen.

Pedro M Folegatti, Katie J Ewer, Parvinder K Aley, Brian Angus, Stephan Becker, Sandra Belij-Rammerstorfer, Duncan Bellamy, Sagida Bibi, Mustapha Bittaye, Elizabeth A Clutterbuck, Christina Dold, Saul N Faust, Adam Finn, Amy L Flaxman, Bassam Hallis, Paul Heath, Daniel Jenkin, Rajeka Lazarus, Rebecca Makinson, Angela M Minassian, Katrina M Pollock, Maheshi Ramasamy, Hannah Robinson, Matthew Snape, Richard Tarrant, Merryn Voysey, Catherine Green, Alexander D Douglas, Adrian VS Hill, Teresa Lambe, Sarah C Gilbert, Andrew J Pollard, Oxford COVID Vaccine Trial Group

Abstract 2
Background: This is the first randomised controlled trial for assessment of the immunogenicity and safety of a candidate non-replicating adenovirus type-5 (Ad5)-vectored COVID-19 vaccine, aiming to determine an appropriate dose of the candidate vaccine for an efficacy study.
Methods: This randomised, double-blind, placebo-controlled, phase 2 trial of the Ad5-vectored COVID-19 vaccine was done in a single centre in Wuhan, China. Healthy adults aged 18 years or older, who were HIV-negative and previous severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection-free, were eligible to participate and were randomly assigned to receive the vaccine at a dose of 1 × 1011 viral particles per mL or 5 × 1010 viral particles per mL, or placebo. Investigators allocated participants at a ratio of 2:1:1 to receive a single injection intramuscularly in the arm. The randomisation list (block size 4) was generated by an independent statistician. Participants, investigators, and staff undertaking laboratory analyses were masked to group allocation. The primary endpoints for immunogenicity were the geometric mean titres (GMTs) of specific ELISA antibody responses to the receptor binding domain (RBD) and neutralising antibody responses at day 28. The primary endpoint for safety evaluation was the incidence of adverse reactions within 14 days. All recruited participants who received at least one dose were included in the primary and safety analyses. This study is registered with, NCT04341389.
Findings: 603 volunteers were recruited and screened for eligibility between April 11 and 16, 2020. 508 eligible participants (50% male; mean age 39·7 years, SD 12·5) consented to participate in the trial and were randomly assigned to receive the vaccine (1 × 1011 viral particles n=253; 5 × 1010 viral particles n=129) or placebo (n=126). In the 1 × 1011 and 5 × 1010 viral particles dose groups, the RBD-specific ELISA antibodies peaked at 656·5 (95% CI 575·2–749·2) and 571·0 (467·6–697·3), with seroconversion rates at 96% (95% CI 93–98) and 97% (92–99), respectively, at day 28. Both doses of the vaccine induced significant neutralising antibody responses to live SARS-CoV-2, with GMTs of 19·5 (95% CI 16·8–22·7) and 18·3 (14·4–23·3) in participants receiving 1 × 1011 and 5 × 1010 viral particles, respectively. Specific interferon γ enzyme-linked immunospot assay responses post vaccination were observed in 227 (90%, 95% CI 85–93) of 253 and 113 (88%, 81–92) of 129 participants in the 1 × 1011 and 5 × 1010 viral particles dose groups, respectively. Solicited adverse reactions were reported by 183 (72%) of 253 and 96 (74%) of 129 participants in the 1 × 1011 and 5 × 1010 viral particles dose groups, respectively. Severe adverse reactions were reported by 24 (9%) participants in the 1 × 1011 viral particles dose group and one (1%) participant in the 5 × 1010 viral particles dose group. No serious adverse reactions were documented.
Interpretation: The Ad5-vectored COVID-19 vaccine at 5 × 1010 viral particles is safe, and induced significant immune responses in the majority of recipients after a single immunisation.
Funding: National Key R&D Programme of China, National Science and Technology Major Project, and CanSino Biologics.

Feng-Cai Zhu, Xu-Hua Guan, Yu-Hua Li, Jian-Ying Huang, Tao Jiang, Li-Hua Hou, Jing-Xin Li, Bei-Fang Yang, Ling Wang, Wen-Juan Wang, Shi-Po Wu, Zhao Wang, Xiao-Hong Wu, Jun-Jie Xu, Zhe Zhang, Si-Yue Jia, Bu-Sen Wang, Yi Hu, Jing-Jing Liu, Jun Zhang, Xiao-Ai Qian, Qiong Li, Hong-Xing Pan, Hu-Dachuan Jiang, Peng Deng, Jin-Bo Gou, Xue-Wen Wang, Xing-Huan Wang, Wei Chen


These data, along with phase I results on Moderna's mRNA vaccine published last week, all suggest that a vaccine – and perhaps more than one – to ameliorate the COVID-19 pandemic may soon be in reach. Looking ahead to phase III trial, which are planned for both these vaccine candidates, MedPageToday quotes Bar-Zeev and Moss note that they should be "rapid, pragmatic, and large enough to address efficacy in subgroups of interest."

Among the most pressing questions a phase III trial should answer include:
Whether a single dose is sufficient in older adults or a booster is required
Does longevity of response or rates of waning differ with a two-dose regimen?
Are there host-specific differences in immunogenicity by age, sex, or ethnicity?

Bar-Zeev and Moss also discussed the need for "pharmacovigilance infrastructure" to monitor the safety of these vaccines, including "surveillance for asymptomatic infection among vaccinated and unvaccinated persons" to determine risk of adverse vaccine outcomes, such as enhanced disease.


The WHO applauded the newly published data but cautioned that it’s still early and further evidence of its effectiveness is needed. CNBC quotes Ryan as saying there are 23 vaccine candidates in clinical development, and until Monday, only one had produced phase one data available in a peer-reviewed journal.

Once one of the vaccines are proven effective, the next challenge will be ensuring there are enough doses to distribute globally, he said. He noted “significant challenges and headwinds” to ensure the vaccines are scaled up to be supplied to as many people as possible.

“That mechanism as it presently stands is not going to be able to supply a vaccine for everybody on the planet,” he said. “We’re going to have to priorities who gets what vaccine at the beginning depending on which vaccine becomes available and we’re going to have to have some policy and priorities around the best use of those vaccines.”


The vaccine could still be ready by the end of the year if scientists can get 50,000 people in trials in the next six weeks, The Daily Telegraph reports experts have said. Initially, it had been hoped that a vaccine might be ready by September, but the number of COVID-19 cases plummeted in Britain after lockdown, meaning the chance of getting infected dropped substantially and making it difficult to test a vaccine.

Researchers were forced to move trials to South Africa and Brazil.

However, Professor Adrian Hill, the director of the Jenner Institute at the University of Oxford, said a jab could yet be ready by December if enough people could be recruited for trials by the beginning of September. "It's possible there will be a vaccine being used by the end of the year," he said. "What that needs is enough cases, probably about 50,000 people to be in trials by six weeks-time, including the very large US trial and to have an adequate incidence, and of course the vaccine has to work.

"But, you know, if it worked by early November – and it might be a little before that – you might have emergency use authorisation in a month, and then you would be deploying in December."


When it comes to protecting the world from the coronavirus, two doses of a vaccine may be better than one. But, Bloomberg Law reports, doubling the number of jabs each person needs could complicate efforts to immunise billions of people.

The latest results from front-runners in the sprint to come up with a vaccine highlight that prospect. Both efforts are conducting final-stage testing with two doses.

Producing vaccines and deploying them to the world’s population in the midst of a pandemic would be a huge challenge even if researchers are able to deliver one-dose inoculations. A need for two would make manufacturing and logistics even more complex.

The report says those challenges would get even tougher if – as some experts think is possible – a vaccine’s efficacy wanes over time and repeat doses are needed, potentially every year. “A one-shot vaccine would be ideal, but the first vaccines are highly unlikely to meet this very high threshold,” said Michael Kinch, a vaccine specialist and associate vice-chancellor at Washington University in St Louis. “As we hopefully move from whether there will be a vaccine to how to apply this, logistics are going to become the absolute most important topics.

Vaccine experts have warned that the first shots to gain approval against COVID-19 might not be the most effective or efficient. In fact, history shows two doses is a more likely scenario. Almost all standard vaccines are multiple-shot regimens, according to Tony Moody, an immunologist at the Duke Human Vaccine Institute. “We would like to do better, and we are all working to get to those better vaccines,” Moody said, “but having something effective soon is the top priority.”


Medical Xpress report


STAT News report


The Lancet abstract 1


The Lancet editorial


The Lancet abstract 2


Full MedPageToday report


Full CNBC report


Full report in The Daily Telegraph


Full Bloomberg Law report


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