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Vaccination decreased measles antibody in plasma donors
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Widespread measles vaccination in the United States has sharply decreased measles antibody titer concentrations in the general population and in plasma donors, according to researchers.
Revaccinating donors only briefly boosted the antibody levels, they wrote in The Journal of Infectious Diseases, highlighting a need for new ways to replenish the donor plasma supply for patients who need it.
“The current screen of plasma donations provided further evidence of the continued decline in measles virus antibody titers in the U.S. plasma donor community, which has now reached a critical level for the supply of intravenous immunoglobulin,” study researcher Thomas R. Kreil, PhD, senior director of Global Pathogen Safety at Shire, and colleagues wrote. “The current study showed that an attempt to boost antibody titers through revaccination cannot be expected to result in a sustainable increase in measles virus antibody titers in plasma donors. It is therefore urgently necessary to consider and investigate alternative measures that will permit for a consistent supply of this important therapeutic.”
Intravenous immunoglobulin (IVIG) is used as an antibody replacement therapy in patients with primary immunodeficiency disorders. The decline in measles antibody titers in donors has made it “increasingly difficult,” the researchers said, to meet FDA potency standards for donated plasma.
To validate previous research indicating that widespread vaccination led to the decreased plasma potency, the researchers assessed results from two snapshot studies. One was conducted in 2007 by CSL Plasma, a company employing several of Kreil’s fellow study authors, and the other in 2015 by BioLife, a plasma services division of Shire.
The 2007 study included 3,312 plasma donations, a portion of which were tested for measles antibody. The 2015 study included 103 samples, which were also tested for measles antibody, and whose donors were later revaccinated. They had donated plasma three to nine times before the study’s start.
Kreil and colleagues found that measles antibody concentrations declined about threefold — from at least 3.5 international units (IU)/mL in donors born before 1962 to a mean of 1.2 IU/mL in donors born after 1968. The 2015 study showed that the mean concentration declined further to 0.5 IU/mL in donors born after 1990. The researchers said that those decreases coincided with the start of widespread measles vaccination in 1963 and that of the two-dose vaccine in 1989.
When the donors enrolled in the 2015 study were revaccinated, their antibody concentrations nearly doubled from a mean of 0.8 IU/mL on the day of revaccination to 1.4 IU/mL after 29 to 45 days. However, in a subset of 20 of those donors, the mean concentration declined to 0.9 IU/mL at 150 days or more after revaccination. A previous study showed similar results, the researchers said.
They concluded that health officials will likely have to change the way they assess antibody potency as they seek to conquer measles globally.
“With the success of the measles vaccination program and the ongoing WHO efforts to eliminate and ultimately eradicate measles worldwide, a replacement of the measles antibody titer as a functional potency requirement for IVIG appears inevitable in the long term,” they wrote. – by Joe Green
Disclosure: Kreil is an employee of Shire. Please see the study for all other authors’ relevant financial disclosures.
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