Second COVID Booster Shot Boosted Antibodies in SeniorsJuly 21, 2022
Anti-spike immunoglobulin G (IgG) antibody titers increased significantly after third and fourth doses of the COVID-19 vaccine in older adults, according to a small study from Israel.
Among 48 participants ages 60 and older who received the Pfizer-BioNTech vaccine, the median IgG titers increased from 450 AU/mL to 27,092 AU/mL a median of 14 days after the third dose, and from 3,775 AU/mL to 28,708 AU/mL a median of 11 days after the fourth dose (P<0.001 for both), reported Noa Eliakim-Raz, MD, of the Rabin Medical Center at Beilinson Hospital in Petah Tikva, and colleagues.
No major adverse events were reported, and no significant correlation was seen between age and IgG titer after the fourth dose (R = -0.041, P=0.78), they noted in a research letter published in JAMA Network Open.
“Data on the response to the fourth BNT162b2 dose among healthy older adults are lacking. Our findings are consistent with those from case series involving patients who received solid organ transplants, in which significant increases in antibody titers and improved humoral response were associated with the fourth BNT162b2 dose,” Eliakim-Raz and team wrote.
After participants received a third dose, which was authorized in July 2021 during the fourth SARS-CoV-2 wave, IgG titers began to wane about 5 or 6 months later, they said, which, along with the emergence of the Omicron variant, led the Israeli Ministry of Health to authorize a fourth dose for people ages 60 and older in January 2022.
They noted that only four participants who received four vaccine doses contracted COVID (P=0.07), and all had asymptomatic to mild infection.
“Booster doses restore protection against infection back to higher levels and incrementally improve protection against severe COVID-19, but frequent booster vaccinations are expensive, inconvenient, and possibly inefficient,” noted Benjamin Cowling, PhD, and Joshua Nealon, PhD, of the University of Hong Kong, in an invited commentary.
“The optimal timing of booster vaccinations is therefore a priority unanswered question for vaccine developers and policy makers alike, aiming to develop and implement vaccination programs that protect people most efficiently as we transition to endemic COVID-19,” they added.
For this analysis, Eliakim-Raz and colleagues included 48 participants (median age 72, 58% women) who had received both a third and fourth vaccine dose. Nearly 70% of participants had dyslipidemia, 50% had hypertension, 31% had obesity, 19% had ischemic heart disease, 17% had type 1 or 2 diabetes, and 2% had congestive heart failure. All patients were seropositive before their fourth dose.
The authors noted that the small sample size and the lack of cellular immunity testing or neutralizing antibody testing were limitations to the study. In addition, they did not examine waning of the immune response after the fourth dose or whether additional boosters would be needed.
Eliakim-Raz reported no disclosures. One co-author reported receiving research grants from Can-Fite BioPharma, AstraZeneca, Bioline RX, Bristol Myers Squibb, Halozyme, Clovis Oncology, CTG Pharma, Exelixis, Geicam, Incyte, Lilly, Moderna, Teva Pharmaceuticals, and Roche and owning stocks and options in CTG Pharma, DocBoxMD, TyrNovo, VYPE, Cytora, and Can-Fite BioPharma.
Nealon reported previously being an employee of and holding shares in Sanofi Pasteur. Cowling reported receiving personal fees from AstraZeneca, Fosun Pharma, GlaxoSmithKline, Moderna, Pfizer, Roche, and Sanofi Pasteur outside the submitted work.