A team of Israeli researchers has found that one dose of the Pfizer COVID-19 vaccine provides 100% protection to youth ages 12-15 within three weeks, raising the question of whether the second dose is necessary.
Injecting a single dose could be considered for young teenagers in Israel “both because the second dose adds relatively little, if any, immunogenicity and we know that for some young people there can be complications like myocarditis,” Prof. Nadav Davidovitch of Ben-Gurion University, who led the research, told The Jerusalem Post.
Tel Aviv University researchers collaborated on the study and although the report has not yet been published, Davidovitch shared a pre-print version with the Post.
The Health Ministry concluded earlier this month that there is a possible link between the second COVID-19 vaccine dose and the onset of myocarditis among young men aged 16 to 30. The link was found to be even stronger in the younger age group of 16- to 19-year-olds. Nonetheless, the ministry has allowed vaccination for youths aged 12-15 and said that anyone seen to be at risk of developing a serious infection, or who lives with someone who has COVID-19, or anyone planning to travel abroad, should get inoculated.
Specifically, the researchers reanalyzed data from the clinical trial of the Pfizer vaccine for ages 12-15 for effectiveness 14 to 20 days after they received the first dose. They found that of 1,130 youth who received the vaccine, two became infected one week after the first dose, one after two weeks, and none after three weeks. Among the youth who received the placebo, there were three infections in week one, four in week two and five in week three.
In other words, the vaccine was 50% effective in preventing COVID-19 within 7-13 days of taking the first dose and 100% effective after 14-20 days.
“Our reanalysis… suggests that for age 12-15 years, effectiveness reached 100% in dose-1, which is the same as dose-2,” the researchers wrote in their report. They said this could be because the vaccines may be more effective for younger people, according to previous studies. In addition, they noted that in the United Kingdom, where at the beginning of the pandemic, administration of the second dose was delayed by up to 86 days to allow more people to get the jab, it was found that the effectiveness of a single vaccine dose continues to rise for at least 60 days.
Davidovitch stressed that the research only applies to Pfizer vaccines and said that more examination is still required to draw any definitive conclusions. However, he said that providing one dose should be considered, especially in countries that have a shortage of vaccines.