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SEPT. 1, 2021

Study shows AstraZeneca vaccine booster dose increases antibodies by a factor of 15

Public Health Undersecretary Paula Daza provided details of the first results of the investigation that began in July, which analyzed immune response to a booster dose.

“We have the first results of the study of a total 127 people over 55 years of age (average age 77) who were given the AstraZeneca vaccine. We observed that the neutralizing antibody titers increased by a factor of 15 compared to the baseline measurement (from 544 to 8,194) in the first 15 days following administration of the booster dose. The study will also provide follow-up results at 30, 60 and 90 days.” 

Public Health Undersecretary Paula Daza explained the first results that have emerged from the study, carried out by the Health Ministry since July. The study analyzes the immune response to a COVID-19 vaccine booster dose. 

It included 523 volunteers, workers at the Public Emergency Assistance Hospital (Posta Central), workers and residents of some long-term residential care homes for Senior citizens (ELEAM), Health Ministry workers and Chilean residents, who completed their COVID-19 vaccination scheme with the Sinovac vaccine before April 15, 2021, and who have no history of natural infection. 

Volunteers received a booster dose of AstraZeneca (127 volunteers); Pfizer (133); or Sinovac (134) at random. 129 people acted as controls or points of comparison. More than half of the volunteers were ELEAM residents or workers. 

Results 

This first stage focuses on results among the over 55 age-group, which is the group that is currently receiving a booster dose. Data will establish whether a booster dose is an appropriate public health measure. This is important among the population that could be at greater risk, such as the elderly, who, in addition to their age, experience greater risk factors due to chronic illnesses. 

“Although there are no studies or evidence that show how many times the base titers of a booster dose should be increased, the study published in Nature shows that a larger number of antibody titers provides greater protection. Our data so far show a significant increase in the neutralizing antibody titers, and that a booster dose will therefore offer a greater level of protection than the complete two-vaccine scheme among the elderly,” explained Johanna Acevedo, head of the Health Ministry’s Health Planning Division (DIPLAS).