Researchers in Spain have conducted the most extensive study to date examining the efficacy of a single dose of health care workers vaccination with Pfizer-BioNTech vaccine to protect against coronavirus disease 2019 (COVID-19).
The team says that one dose of the vaccine stimulated a much stronger antibody response against the causative agent – coronavirus 2 (SARS-CoV-2) acute respiratory syndrome – among health care workers who had previously contracted the virus. this than among those who did not.
The researchers say that with the controversy over how to ensure that vaccination is appropriate in the population in times of vaccine shortage, the findings of the study may help make decisions about giving one. dose only in some cases.
“To date, this is the largest study examining the immune response after a single dose of the Pfizer-BioNTech BNT162b2 vaccine,” wrote Maria Velasco of Alcorcon Foundation University Hospital in Madrid and her colleagues. “These data may prioritize an increased dose in times of vaccine shortage.”
A pre-printed version of the research paper can be found on the medRxiv* server, while the article is subject to peer review.
The current challenges facing the control of COVID-19
Currently, the primary means of controlling COVID-19 pandemic disease is the distribution of recently approved vaccines and adherence to social distance and hygiene practices.
However, limited supply of vaccines is a challenge in ensuring that a sufficient proportion of the population is vaccinated in order to achieve herd immunity.
The standard immunization protocol for the Pfizer-BioNTech vaccine is a 2-dose regimen separated by between 3 and 4 weeks.
However, a one-dose schedule for some people who do not need an elevated bullet may help to ensure that herd immunity is achieved in the event of a vaccine deficiency.
Velasco and colleagues say data on immune responses to a single dose of the Pfizer-BioNTech vaccine are currently limited to a few observational studies with a small number of patients.
“Furthermore, little is known about the effects of previous natural infections on vaccine response,” they add.
What did the researchers do?
The team studied a single-dose-induced antibody response of the Pfizer-BioNtech BNT162b2 vaccine among 641 health care workers (mean age of 45.8 years) who had previously participated in the SARS-CoV-2 seroprevalence study made in April and November of 2020.
Participants were divided into three groups, according to which they were seronegative for the virus in both studies (SARS-CoV-2 naïve); transient seropositive (positive in the first study, but not the second) or continuous seropositive (positive in both studies).
Seropositive individuals were further divided by COVID-19 severity into those with asymptomatic disease, those with moderate to severe outpatient treatment on an outpatient basis, and those with very severe disease requiring recurrence. to the hospital.
Blood samples were taken from the participants after receiving one dose of the vaccine and immediately before receiving the second dose (21 days after the first dose).
The samples were tested for immunoglobulin (IgG) antibodies against SARS-CoV-2 superficial proteins called spike. The spike protein is the main structure used by the virus to bind host cells and a key target of the neutral antibodies that cause infection or immunization.
What did the study find?
The moderate anti-spike IgG titer induced by a single vaccine dose was approximately 20 times higher among pre-existing seropositive participants (22,267.3 resolution units) [AU]/ mL) than among naïve SARS-CoV-2 participants (median 1,022.3 AU / mL).
Compared with naïve SARS-CoV-2 participants, moderate anti-spike IgG titers were approximately 4 times higher among transgender seropositive individuals (3,860.0 AU / mL) and approximately 34 times higher among advanced human beings (34,551.6 AU / mL).
Among those seropositive, the level of disease anxiety was also associated with anti-spike IgG titers. The median titer for asymptomatic disease was 15,386.4 AU / mL, compared with 24,388.8 AU / mL for moderate to severe infection and 43,671.7 AU / mL for severe disease.
“Our serological assessment of health care workers showed a surprisingly different response 3 weeks after a single dose of the BNT162b2 vaccine, as seen previously on SARS-CoV2 and serological status,” wrote Velasco and colleagues.
The combination of previous clinical COVID-19 and the presence of anti-spike IgG antibodies prior to vaccination were strong predictors of a strong serologic response to a single vaccine dose, the team says.
What do the authors suggest?
“Our findings suggest that delaying a second dose of the vaccine may not be a high-risk strategy for some people with a strong serologic response,” the researchers said.
This would allow the vaccination of other at-risk individuals to allow adequate vaccination to follow the standard, clinically proven protocol (two doses 3 to 4 weeks apart).
* Important message
medRxiv publish preliminary scientific reports that are not peer-reviewed and, therefore, should not be seen as final, guiding health-related clinical practice / behavior, or be treated as information established.