COVID-19 Roundup: Fourth Vaccine Dose, Menstrual Cycles and Vaccination, Multivariant Booster, Pediatric COVID-19 Vaccine Boosters

Fourth COVID-19 Vaccine Dose1

A fourth dose of a COVID-19 vaccine may produce a 5-fold increase in the number of antibodies 1 week following vaccination, according to the preliminary results of an ongoing study.

Based out of Sheba Medical Center in Israel, the study includes 150 health care workers who received their third COVID-19 dose 4 to 5 months ago. All participants received the Pfizer-BioNTech booster dose, although a second group is to receive Moderna booster doses in the coming days.

Israel is currently administering fourth doses to individuals aged older than 60 years, health care workers, and immunocompromised individuals. However, the World Health Organization has stated that more people globally need to be vaccinated with first doses before recommending boosters to fully vaccinated individuals.

Vaccination and Menstrual Cycle2

Women vaccinated against COVID-19 during their menstrual cycle may experience a small increase in cycle length when compared with unvaccinated women, according to the results of a recent study.

The researchers utilized data from Natural Cycles, a fertility tracking app, to analyze 6 consecutive cycles for unvaccinated women, and 3 consecutive cycles before vaccination and 3 consecutive cycles after for vaccinated women.

The results indicated that there was a 0.71-day cycle increase associated with the first vaccination dose, and a 0.91-day increase associated with the second vaccination dose on average. However, this increase in cycle length was not associated with a change in the number of days of menstrual bleeding for vaccinated individuals.

The International Federation of Gynecology and Obstetrics defines a variation of cycle length as “normal” if the change is less than 8 days.

Multivariant COVID-19 Booster3

A multivariant COVID-19 vaccine booster may provide a strong level of neutralizing antibodies similar to that of mRNA vaccines, according to the preliminary results of a phase 1 clinical trial.

The vaccine, produced by Gritstone Bio Inc., is a self-amplifying mRNA (samRNA) second-generation vaccine that is administered in a single dose of 10 µg at least 22 weeks following 2 doses of the AstraZeneca vaccine. No grade 3/4 adverse events have been reported so far. The clinical trial has recently been authorized to expand from 20 trial participants to 120 trial participants.

“We are thrilled to share that our T cell-enhanced samRNA vaccine from the CORAL program is driving both robust CD8+ T cell responses to abroad array of viral epitopes and strong neutralizing antibody responses to Spike, which we believe validates the potential of our infectious disease platform,” president and chief executive officer of Gritstone Andrew Allen, MD, PhD, concluded.

Pediatric Booster Doses4

The US Food and Drug Administration (FDA) has amended the emergency use authorization to allow individuals aged 12 to 15 years to receive a single booster dose of the Pfizer-BioNTech COVID-19 vaccine.

The FDA also reduced the time required between the primary series and booster dose administration for all individuals aged 12 years or older. Individuals may now receive a booster dose 5 months following completion of the primary vaccine series instead of 6 months.

Further, certain immunocompromised pediatric populations are now eligible for a third primary series dose. Included are individuals aged 5 to 11 years who have undergone solid organ transplantation or are diagnosed with conditions with similar levels of immunocompromise, and those who may not produce sufficient immune responses to the 2-dose primary series.


—Leigh Precopio



  1. Heller J, Lubell M. Fourth COVID-19 vaccine dose boosts antibodies five-fold in Israeli study, PM says. Reuters. January 4, 2022. Accessed January 7, 2022. 
  2. Edelman A, Boniface ER, Benhar E, et al. Association between menstrual cycle length and coronavirus disease 2019 (COVID-19) vaccination: a US cohort. Obstet Gynecol. Published online January 5, 2022.
  3. Early data for multivariant COVID-19 vaccine booster shows promise. News release. The University of Manchester; January 4, 2022. Accessed January 7, 2022.
  4. Coronavirus (COVID-19) Update: FDA takes multiple actions to expand use of Pfizer-BioNTech COVID-19 Vaccine. News release. US Food and Drug Administration; January 3, 2022. Accessed January 7, 2022.