Single dose of Pfizer vaccine reduces risk of SARS-CoV-2 infection in kids

As of March 17, 2022, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which is the virus responsible for the coronavirus disease 2019 (COVID-19), has infected over 464 million and caused almost 6.1 million deaths. Early on in the COVID-19 pandemic, researchers around the world races to develop safe vaccines against SARS-CoV-2, which led to the development of two messenger ribonucleic acid (mRNA) vaccines in December 2021, followed by several other vaccines based on other platforms.

In a new study published on the medRxiv* preprint server, researchers discuss the efficacy of COVID-19 vaccines in young people and children when the SARS-CoV-2 Delta and Omicron variants were the dominant circulating strains.

Study: Vaccination Against SARS-Cov-2 In UK School-Aged Children and Young People Decreases Infection Rates and Reduces COVID-19 Symptoms. Image Credit: Studio Romantic / Shutterstock.com

Study: Vaccination Against SARS-Cov-2 In UK School-Aged Children and Young People Decreases Infection Rates and Reduces COVID-19 Symptoms. Image Credit: Studio Romantic / Shutterstock.com

This news article was a review of a preliminary scientific report that had not undergone peer-review at the time of publication. Since its initial publication, the scientific report has now been peer reviewed and accepted for publication in a Scientific Journal. Links to the preliminary and peer-reviewed reports are available in the Sources section at the bottom of this article. View Sources

Introduction

Earlier studies have explored the transmission of SARs-CoV-2 among children stratified by age, seroprevalence rates in this age group, as well as the clinical aspects of the infection among children. Vaccination studies were examined in other studies and included information on specific pediatric disease cohorts and the relationship between vaccination and disease severity.

The mRNA vaccines were tested in clinical trials in minors and found that most symptoms among the vaccinated were mild and transient. In the current study, multiple components of the United Kingdom vaccination campaign for children and young people (CYP) aged 12-17 years were evaluated based on a single dose of the Pfizer mRNA vaccine.

The current study used data from over 100,000 CYP who used the Covid Symptom Study (CSS) app to report their symptoms. The aim was to determine the risk of infection after vaccination with a single dose and the intensity of disease in those who experienced breakthrough infections.

Study findings

The first vaccine dose was found to protect CYP against both Delta and Omicron infection, with the effect being more robust in individuals with a history of a prior SARS-CoV-2 infection. The researchers also found that disease symptoms were milder in those infected after vaccination as compared to unvaccinated and infected CYP.

Infection risk reduction after single vaccination with BNT162b2 in 12- to17-year-old CYP during periods of Delta (left) and Omicron (right) variant predominance in UK. Bars represent risk reduction at 14-30 days, 1-2 months, and 2-3 months for post-vaccination infection, compared with unvaccinated CYP. The black lines show 95% CIs. Number of observations (i.e., tests) of CYP aged 12-17 years: for period of Delta variant predominance n (test) =15,308 (4,793 unvaccinated, 10,515 vaccinated); for period of Omicron variant predominance n (test)=8,203 (930 unvaccinated, 7,273 vaccinated).

Infection risk reduction after single vaccination with BNT162b2 in 12- to17-year-old CYP during periods of Delta (left) and Omicron (right) variant predominance in UK. Bars represent risk reduction at 14-30 days, 1-2 months, and 2-3 months for post-vaccination infection, compared with unvaccinated CYP. The black lines show 95% CIs. Number of observations (i.e., tests) of CYP aged 12-17 years: for period of Delta variant predominance n (test) =15,308 (4,793 unvaccinated, 10,515 vaccinated); for period of Omicron variant predominance n (test)=8,203 (930 unvaccinated, 7,273 vaccinated).

During the study period between August 5, 2021, and February 14, 2022, approximately 26, 000 CYP were vaccinated with a single dose of the Pfizer vaccine. Over the next 14-30 days, the risk of infection dropped 80% for Delta and about 54% for Omicron variants. At two to three months after vaccination, the risk of infection further declined by about 62% and 64%, for the Delta and Omicron variants, respectively.

During the Delta-dominant period, the reduction in risk after vaccination was higher than that which was recorded during the Omicron period for at least the first three months in adolescents aged 16-17 years and at least two months post-vaccination in those aged 12-15 years. During the Delta-dominant period, the probability of being risk-free was over 90% for the first 11 weeks and fell just below 90% at 90 days.

Conversely, during the Omicron-dominant period, the chances of remaining free of infection were greater than 90% at 30 days, and greater than 80% at 40 days. The risk of infection was significantly lower among those with prior infection and was close to zero at 100 days and beyond.

Following vaccination, SARS-CoV-2 infection during the Delta-dominant period was markedly milder as compared to those who were unvaccinated, though this was seen only in children aged 12-15 years during the Omicron-dominant period. This applied to respiratory, neurological, and systemic symptoms, except runny nose and sneezing. During the Omicron-dominant period, a persistent cough and hoarse voice were the only exceptions to the generally reduced prevalence of symptoms.

However, both for vaccinated and unvaccinated children who were infected with the Delta or Omicron variants, the median duration of symptoms was less than a day. Young people occasionally had skin lesions like blisters or weals, and soreness of the eyes, which lasted more than a day in most cases.

Less than 2% of CYP visited the hospital over the entire study period, vaccinated or unvaccinated. Post-vaccination symptoms were very mild, mostly local, and self-resolving in the majority of cases. Systemic side effects were rare and also resolved quickly.

Implications

The results of the current study demonstrate that a single dose of the Pfizer vaccine in CYP is generally safe and well-tolerated. One vaccine dose reduced the risk of subsequent infection with SARS-CoV-2 in children aged 12-15 years beginning 14 days from the day of vaccination.

This protective benefit was found to be greater against the SARS-CoV-2 Delta variant as compared to the Omicron variant. In the case of vaccinated children who had a history of prior SARS-CoV-2 infection, the protection was over 90% against reinfection for 100 days or more. According to current models, more than 90% of children in the U.K. are considered to have been previously infected with SARS-CoV-2.

Using a risk-benefit analysis, the researchers conclude that there was quantitative evidence to support the rationale for immunization of this group. This supports earlier studies showing vaccine-mediated protection against reinfection with the SARS-CoV-2 wildtype, Alpha, and Delta variants, though to a lesser extent against the Omicron variant. Furthermore, a single vaccine dose was found to reduce disease severity in case of breakthrough infection.

Since the current study was carried out during the period when both the Omicron and Delta were circulating, its results may also be specific to these variants. COVID-19 in children is typically a mild, short-lived disease; therefore, the ability to discriminate between naturally mild disease and vaccine-mediated reduction in the severity of the disease is limited.

Even though most recommendations are for two-dose immunization of children, “our data suggest some nuance may be appropriate regarding recommendations for second-dose vaccination, considered temporally (particularly with reference to prior infection) and to new variant emergence.”

This news article was a review of a preliminary scientific report that had not undergone peer-review at the time of publication. Since its initial publication, the scientific report has now been peer reviewed and accepted for publication in a Scientific Journal. Links to the preliminary and peer-reviewed reports are available in the Sources section at the bottom of this article. View Sources

Journal references:

Article Revisions

  • May 12 2023 - The preprint preliminary research paper that this article was based upon was accepted for publication in a peer-reviewed Scientific Journal. This article was edited accordingly to include a link to the final peer-reviewed paper, now shown in the sources section.
Dr. Liji Thomas

Written by

Dr. Liji Thomas

Dr. Liji Thomas is an OB-GYN, who graduated from the Government Medical College, University of Calicut, Kerala, in 2001. Liji practiced as a full-time consultant in obstetrics/gynecology in a private hospital for a few years following her graduation. She has counseled hundreds of patients facing issues from pregnancy-related problems and infertility, and has been in charge of over 2,000 deliveries, striving always to achieve a normal delivery rather than operative.

Citations

Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Thomas, Liji. (2023, May 12). Single dose of Pfizer vaccine reduces risk of SARS-CoV-2 infection in kids. News-Medical. Retrieved on June 21, 2024 from https://www.news-medical.net/news/20220317/Single-dose-of-Pfizer-vaccine-reduces-risk-of-SARS-CoV-2-infection-in-kids.aspx.

  • MLA

    Thomas, Liji. "Single dose of Pfizer vaccine reduces risk of SARS-CoV-2 infection in kids". News-Medical. 21 June 2024. <https://www.news-medical.net/news/20220317/Single-dose-of-Pfizer-vaccine-reduces-risk-of-SARS-CoV-2-infection-in-kids.aspx>.

  • Chicago

    Thomas, Liji. "Single dose of Pfizer vaccine reduces risk of SARS-CoV-2 infection in kids". News-Medical. https://www.news-medical.net/news/20220317/Single-dose-of-Pfizer-vaccine-reduces-risk-of-SARS-CoV-2-infection-in-kids.aspx. (accessed June 21, 2024).

  • Harvard

    Thomas, Liji. 2023. Single dose of Pfizer vaccine reduces risk of SARS-CoV-2 infection in kids. News-Medical, viewed 21 June 2024, https://www.news-medical.net/news/20220317/Single-dose-of-Pfizer-vaccine-reduces-risk-of-SARS-CoV-2-infection-in-kids.aspx.

Comments

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
Post a new comment
Post

While we only use edited and approved content for Azthena answers, it may on occasions provide incorrect responses. Please confirm any data provided with the related suppliers or authors. We do not provide medical advice, if you search for medical information you must always consult a medical professional before acting on any information provided.

Your questions, but not your email details will be shared with OpenAI and retained for 30 days in accordance with their privacy principles.

Please do not ask questions that use sensitive or confidential information.

Read the full Terms & Conditions.

You might also like...
New strategy targets rare B cells for effective HIV vaccine development