COVID-19 antibodies produced by the Pfizer vaccine dropped by more than 80 percent in senior nursing home residents and their caregivers six months after receiving their second dose, a US study found.
The study, led by Case Western Reserve University and Brown University in the US, studied blood samples from 120 nursing home residents and 92 health professionals.
The researchers mainly looked at humoral immunity — also called antibody-mediated immunity — to measure the body’s defenses against the SARS-CoV-2 virus, which causes COVID-19.
The yet-to-be-published study, published on the preprint server medRxiv, found that individuals’ antibody levels dropped by more than 80 percent after six months.
The results were the same in seniors, with a median age of 76, and caregivers, with a median age of 48, and old, the researchers said.
The team’s previous research found that seniors who had not previously contracted COVID-19 already showed a decreased antibody response within two weeks of receiving the second dose of vaccine that was significantly lower than the younger caregivers experienced.
Six months after vaccination, the blood of 70 percent of these nursing home residents had “a very poor ability to neutralize the coronavirus infection in lab experiments,” said David Canaday, a professor at Case Western Reserve University.
The results support the Centers for Disease Control and Prevention’s (CDC) recommendation for booster shots — especially for the elderly — because of declining immunity, Canaday said.
The study noted that the boosters are even more important as the Delta variant spreads.
Early in the pandemic, higher COVID-19 deaths among nursing home residents in the US led them to become a priority for vaccination, the researchers said.
Most nursing home residents received the Pfizer vaccine under the emergency use authorizations because it was the first available vaccine on the market, they said.
“With the poor initial vaccine response of nursing home residents, the rise of breakthrough infections and outbreaks, characterization of immunity durability is needed to inform public health policy about the need for reinforcement,” the study authors added.
(Except for the headline, this story has not been edited by NewsMadura staff and has been published from a syndicated feed.)