The latest COVID vaccine developments
AstraZeneca safety update
Many people have believed the AstraZeneca vaccine to be in some ways inferior to the Pfizer or Moderna alternatives. The vaccine was bedevilled by safety concerns in the early days of the pandemic. However, most clinicians consider the risk of serious illness from COVID far outweighs the risks associated with the vaccine.
Now in another large and robust clinical trial across North and South America the AstraZeneca vaccine has again been shown to be safe and effective.
In an ongoing, double-blind, randomised, placebo-controlled trial (the absolute gold standard of clinical evaluation) including 32,451 participants, the vaccine has again delivered impressive results.
Furthermore, the trial included a diverse population of older adults who have been associated as being at increased risk from possible side-effects from the vaccine.
The Phase 3 trial investigated the safety, vaccine efficacy and immunogenicity (the strength of immune response over time) of two doses of the vaccine, compared with a placebo. Two-thirds of the cohort were given the vaccine (21,635) and one third were given a placebo (10,816).
The results of the trial
The vaccine was proven to be safe with low incidences of serious adverse events – a similar rate of adverse events was observed amongst the placebo group. The overall vaccine efficacy was 74%, although was 83.5% amongst those aged 65 or older.
No severe or critical symptomatic cases of COVID-19 were observed amongst the AstraZeneca Group whilst eight were observed in the placebo (unvaccinated) group.
Pfizer protection drops after six months
Israel was one of the first countries in the world to achieve a high rate of vaccination amongst the population. However, despite high vaccine coverage the rate of COVID-19 infection has been increasing.
One team of scientists at the Gertner Institute of Epidemiology in Israel conducted a six month study tracking healthcare workers who had been vaccinated. The workers were tested monthly for both types of antibodies (IgG and neutralising antibodies) that the body produces to fight viruses.
The study tracked 4,868 participants and found that levels of IgG antibodies decreased at a consistent rate, whilst the neutralising antibodies decreased at a rapid rate for the first three months.
Six months after being given a second dose of the Pfizer vaccine, neutralising antibody levels were substantially lower among men than among women. They were also lower amongst those aged 65 and over when compared to those aged 18 to 45.
Is a universal coronavirus vaccine possible?
Emerging variants pose a threat to the effectiveness of current COVID vaccines. Some COVID vaccines can be adapted fairly quickly, but new trials will be necessary to prove they are safe and effective.
As well as emerging variants, new types of coronavirus may well appear, in the same way as SARS-CoV-1, MERS and SARS-CoV-2.
There are hundreds of SARS-CoV strains known to infect different non-human species. Coronaviruses are considered zoonotic (they can jump between species) and the subgenus of Sarbecoviruses are gaining a notorious history of jumping from animals to humans.
Exact evolutionary transmission has not been determined, but bats, pangolins, and civets are believed to play a role in transmission to humans.
A vaccine that could prevent infection cased by known and future variants of concern, as well pre-emergent sarbecoviruses (those with the potential to cause disease in humans in the future) could be utterly transformative for world health.
A “third generation” vaccine
Now a research team at the National University of Singapore have demonstrated it may, in theory, be possible to create such a dream vaccine.
The team managed to elicit data from a very small cohort of patients that showed potent pan-sarbecovirus (so attacking all know and possible covid’s) neutralising antibodies could be induced amongst survivors of SARS-CoV-1, who were immunised with the Pfizer BioNTech vaccine.
The antibodies they elicited were capable of neutralising all known variants of concern but also sarbecoviruses identified in bats and pangolins that have the potential to infect humans. That in turn demonstrated that a pan-sarbecovirus strategy may be feasible.
Sadly, the investigation was based on less than 50 samples obtained from five different groups of patients and it is not possible to rule out confounding factors, such as the different ages of the patients, for example. That means the theory has not been proved, just that the hypothesis has passed the first “could this even work?” stage.
Much more scientific evaluation needs to be done, however, If successful, this will lay a strong foundation for the development of a third-generation Covid-19 vaccine. This offers the hope that current and emerging variants of concern could be readily controlled, as well as for preventing future sarbecovirus viruses from becoming pandemics.
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