Booster Shots, Efficacy of COVID-19 vaccines

Clinical studies showed that mRNA vaccines developed by Pfizer-BioNTech and Moderna were initially over 90 percent effective against severe COVID-19 disease.

The Johnson & Johnson vaccine was found to be a little less effective, but still very protective against hospitalization.

However, researchers at the University of California at San Diego wrote in the New England Journal of Medicine last week, the efficacy of the mRNA vaccine against symptomatic cases of COVID-19 had dropped to 65% by July 2021, with the drop being attributed to waning efficacy over time.

“The decline in efficiency is not entirely surprising,” said Dr Francesca Torriani, Professor of Clinical Medicine in the Division of Infectious Diseases and Global Public Health at UC San Diego School of Medicine, and Director of the Infection Prevention and Clinical Epidemiology Program at UC San Diego Health .

“Data from clinical trials suggest that a decrease in efficacy would occur several months after full vaccination, but our results indicate that compared to the Delta variant, the efficacy of the vaccine for mildly symptomatic illnesses was considerably lower and decreased 6 to 8 months after the end of vaccination, ”explained Torriani.

Jonathan H. Watanabe, PharmD, PhD, a COVID-19 health outcomes researcher and associate dean of evaluation and quality at the University of California at Irvine, told Healthline that research shows that the effectiveness of vaccines in MRNA appears to decrease by about 6% every 2 months.

Meanwhile, a to study Israel concluded that a third booster injection of the mRNA vaccines appeared to significantly restore the protective effects.

“We found that 7 to 13 days after the booster, there is a 48-68% reduction in the chance of testing positive for SARS-CoV-2 infection, and that 14 to 20 days after the booster, marginal efficiency increases to 70-84 percent, ”researchers from Maccabi Healthcare Services reported.

“There is not much to discuss in terms of … giving an antibody booster against the most prevalent [Delta] variant, ”Watanabe said.

In mid-August, the US Department of Health and Human Services (HHS) announcement plans to offer COVID-19 reminders to people who had previously received both doses of the Pfizer or Moderna vaccines.

Officials have raised concerns that the vaccine’s effectiveness “may decline in the coming months, especially among those who are at higher risk or who were vaccinated in the early stages of the rollout. vaccination”.

“The available data show very clearly that the protection against SARS-CoV-2 infection begins to wane over time after the initial vaccination doses, and in association with the dominance of the Delta variant, we are starting to see evidence of reduced protection against mild infections. and moderate illness, ”according to the policy statement released by the HHS.

HHS officials said the booster shots would be available from the week of September 20.

Priority will be given to those who received their first doses of mRNA vaccines 8 months earlier, “including many health care providers, nursing home residents and other elderly”, as well as residents of long-term care facilities, according to the HHS.

Unlike the first mRNA deployment in early 2021, age will not directly determine the priority of booster injections.

However, Americans who received their initial vaccine as soon as it was available to people aged 65 and over would still be among the first to be eligible for booster shots.

Vaccine weakening studies have not been able to determine whether or not protection weakens more quickly in people over 65 years of age.

The study from Israel suggested that efficacy in the elderly declined more than among other age groups. But one New York study published by the Centers for Disease Control and Prevention (CDC) found no such disparity.

Booster shots for recipients of the Johnson & Johnson vaccines “will likely be needed,” according to the HHS, although the timing differs as administration of this vaccine did not begin until March 2021.

Other booster shots may also be needed until more of the population is vaccinated and new variants continue to develop thanks to the uncontrolled spread of the disease in the community, Watanabe said.

“The reality of this vaccine is that until we really hit that herd immunity of 70% or more, we’re going to keep doing it,” he said.

Watanabe cautioned against finding that COVID-19 vaccines don’t work just because booster shots are recommended.

Flu shots are needed every year, he noted, and booster shots are common for many other commonly given vaccines, including tetanus, hepatitis and measles.

“Although efficacy may have declined, vaccines still provide very effective protection against severe disease COVID-19,” he said.