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This week, AstraZeneca released two sets of phase III safety trial results for its Covid-19 vaccine, each showing slightly different efficacy prices . The inconsistency has kicked up controversy and confusion, but experts so far believe there’s little effect on safety.

The results

In AstraZeneca’s initial set of data, released March 22nd, its vaccine candidate was demonstrated to be 79% effective overall and 80% effective on adults 65 and older, This report, based on 32,449 trial participants with a 2:1 distribution of vaccine to placebo, had 141 instances of Covid-19. None were acute , despite 20% of subjects being in the 65-and-older age group and 60% overall with comorbidities that increased Covid-19 risk.

Later in the week, another set of data was released. Now, the effectiveness was just 76% overall but had climbed to 85 percent for patients aged 65 and older. 49 more cases were included, bringing the total to 190. Eight of these cases were severe, but they had received the placebo rather than the vaccine. The new report also cites 14 more unconfirmed instances that could shift the percentage more as analysis persists .

Bridging the gap

As to what happened between the first and second release of data , AstraZeneca released two sets of information so close together, complicated.

AstraZeneca’s initial results raised the eyebrows of these federal officials involved in reviewing AZ’s trial information . The New York Times reported that the trial’s federal medical supervision board sent a private letter into the pharma giant criticizing its report for using an incomplete set of results . Some recent Covid-19 cases were excluded after discussion with the board, improving the quoted efficacy rate. Soon after, the National Institute of Allergy and Infectious Diseases issued a statement on the controversy:

“Late Monday, the Data and Safety Monitoring Board (DSMB) [sent notification] that it was concerned by data released by AstraZeneca on first data from the COVID-19 vaccine clinical trial … [and] could have included obsolete information from that trial, which could have provided an incomplete view of the effectiveness data. ” 

The board requested up-to-date info , which became the second round of phase III trial results.

In the companys press release, Executive Vice President of BioPharmaceuticals R&D Mene Pangalos explained : The main analysis is consistent with our previously published interim analysis and confirms that our COVID-19 vaccine is highly effective in adults, such as those aged 65 years and above . We anticipate submitting our regulatory submission for Emergency Use Authorization in the US and preparing for the rollout of millions of doses across America. ”

Blood clot concern

The AZ vaccine made headlines earlier in the month to get a different issue . In early March, the Federal Office for Safety in Health Care (BASG) received reports of two cases of death by blood clot in patients that had received doses from the same batch of AZ disease . Countries across Europe temporarily suspended usage of this vaccine.

The European Medicines Agency ran an investigation to the accounts and concluded that many people had no significant risk of blood clots. Clotting was a “very infrequent ” potential reaction in patients with low levels of blood platelets.  

Still safe and effective?

In the wake of the blood clot warnings, the WHO issued its comment, stating “ it is routine for countries to indicate potential adverse events following immunization. This does not necessarily imply that the events are connected to vaccination itself, but it is good practice to research them. ” The WHO believes that “the advantages of the AstraZeneca vaccine outweigh its risks and recommends that vaccinations continue. ”

Health Canada added a warning regarding the blood clot risk to its advice , but is still advocating people move forward with using all approved vaccines. No risk of blood clots was listed in the clinical trial results released in the united states .

As for the difference in trial outcomes ? There may not be cause for concern. Stephen Evans BA, MSc, FRCP, of the vaccine center at London School of Hygiene and Tropical Medicine, told the Associated Press any vaccine with over 60% effectiveness could be important adding that, “Results fluctuate as data collect … what counts will be the FDA assessment and that will be done based on evaluation of the full data and not press releases. ”

According to its press releases, AstraZeneca intends to apply for FDA Emergency Use Authorization “in the coming weeks. ”

Sean Marsala is a health writer based in Philadelphia, Pa.. Passionate about technology, he can usually be found reading, browsing the internet and exploring virtual worlds.

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