COVID-19 vaccine manufacturer and developer AstraZeneca acknowledged on Wednesday that there were some errors in giving shots to the participants during the last stage trial.

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SYDNEY, AUSTRALIA - AUGUST 19: A general view of AstraZeneca is seen during Prime Minister Scott Morrison's visit on August 19, 2020 in Sydney, Australia. The Australian government has announced an agreement with the British pharmaceutical giant AstraZeneca to secure at least 25 million doses of a COVID-19 vaccine if it passes clinical trials.

COVID-19 vaccine is instrumental in fighting the pandemic. Manufacturers and developers must make sure that it is safe, effective, and will give lifetime immunity against the virus. This is the reason why vaccines must undergo three different stages of human clinical trials. 

This is also the reason why the different health experts including the independent panel of the U.S. Food and Drug Administration previously asked the demographics of the participants, because it would affect how the COVID-19 works for different individuals and races. 

Blunder during the testing

According to The Telegraph, Oxford University and AstraZeneca acknowledged on Wednesday that some vials used in the trial did not have the right concentration of vaccine. This means that some volunteers received half-dose while others received two full doses. 

Due to this manufacturing issue, many experts now question the results of their experimental COVID-19 vaccine.

The issue came after Oxford University and AstraZeneca said that their shots are highly effective. However, they did not mention and explain why some of their participants did not receive the same shots.

There were a group of volunteers who received a lower dose while others received two full doses. AstraZeneca said that those who received lower doses appeared to have 90 percent protection against the virus while those who received two full shots received 62 percent.

Even though the COVID-19 vaccine manufacturers said that their vaccine is 70 percent effective, some experts raised some questions about the safety of the vaccine. Specifically, they questioned how many of the participants received half and full dose. 

Read also: Oxford, AstraZeneca's COVID-19 Vaccine Found Safe for Older Adults 

The result that was announced on Monday were from large ongoing studies in the UK and Brazil designed to determine the optimal dose of vaccine, as well as examine safety and effectiveness.

They tried multiple doses on the volunteers then compared to those who were given a meningitis vaccine or a saline shot.

Moreover, Oxford University and AstraZeneca explained before they begin their research on how they are going to implement and analyze the results. They also said at that time that any deviation from that protocol can put the results in question. 

Researchers from Oxford University said that some vials used during the trials did not have the right concentration or some volunteers only got a half dose. They also clarified that they already discussed this with the regulators and agreed to complete the late-stage trial with two groups. 

Another problem that also raised concern to the experts is that one of the participants in the low-dose group was 55 years old and above.

It is already a common assumption that younger people tend to develop a stronger immune response than older people. 

Experts added that it could be the reason why the results of their COVID-19 vaccine seems to be effective.

David Salisbury also said another point of confusion comes from a decision to pool results from two groups of participants who received different dosing levels to reach an average of 70 percent effectiveness.

Read also: Moderna's COVID-19 Vaccine: How Much Does It Cost Per Dose?