During the AstraZeneca trial last year, researchers made an unfortunate dosing error. Now scientists have found that this incident has increased the effectiveness of the new type of coronavirus vaccine.

In a trial of the AstraZeneca vaccine last year, more than 1,000 participants accidentally received half of the drug during their first vaccination. However, by the end of the trial, it appeared that such patients potentially received better protection from the virus than those who received two standard doses. It quickly became clear that the half-dose protocol was actually a mistake and not a deliberate plan.

In a new study, Northwestern Medicine experts repeated the protocol and showed that some vaccines are more effective when the first dose is much lower than the second.

To investigate this question, the researchers studied the immune responses in mice to two different COVID-19 vaccines, CanSino and Sputnik V. Both are serotype 5 adenovirus vaccines, using the same viral vector as AstraZeneca.

The study reported that the initial low dose followed by a higher dose escalation caused a significantly better immune response in mice, both qualitatively and quantitatively, compared to the two high doses. The researchers also saw similar benefits of low / high doses of an experimental HIV vaccine that uses the same adenoviral vector as COVID-19 vaccines. This indicates that the low/high dose protocol may be useful with other vaccines.