Influenza

Flublok by Protein Sciences Corporation (Quadrivalent Influenza)

Captured 2022-12-09

Document Highlights

Initial U.S. Approval: 2013

Flublok Quadrivalent is a vaccine indicated for active immunization against disease caused by influenza A subtype viruses and influenza type B viruses… approved for use in persons 18 years of age and older.

Among adults 50 years of age and older (Study 2), 20 deaths occurred in the 6 months post-vaccination, including 8 Flublok Quadrivalent and 12 Comparator [vaccine] recipients.

SAEs [serious adverse events] were reported by… 3.4%…

In the 28 days following vaccination, one or more unsolicited treatment emergent adverse events occurred in 10.3% of Flublok Quadrivalent… recipients in Study 1 (adults 18-49 years of age) and in 13.9% of Flublok Quadrivalent… recipients in Study 2 (adults ≥50 years of age).

Postmarketing Experience
– anaphylaxis, allergic reactions, and other forms of hypersensitivity (including urticaria).

Flublok… contains purified HA proteins produced in a continuous insect cell line… derived from… cells of the fall armyworm, Spodoptera frugiperda (which is related to moths, caterpillars and butterflies)…

A single 0.5 mL dose… contains…polysorbate 20… may also contain residual amounts of baculovirus and Spodoptera frugiperda cell proteins… baculovirus and cellular DNA…

Comments

The trivalent formulation of Flublok was tested in one study on 18-49 year olds against a saline placebo:

"Study 3 included 4648 subjects 18 through 49 years of age for safety analysis, randomized to receive Flublok (n=2344) or placebo (n=2304)."

"SAEs [serious adverse events] were reported by 32 Flublok recipients and 35 placebo recipients."

The manufacturer claims the control group received a saline placebo (a mostly inert, low bioactive substance), yet collected more serious adverse event reports by placebo recipients than trivalent Flublok recipients.

It is not clear in the insert, nor in the clinical trial (Study 3) how long serious adverse events were collected post-vaccination, however unsolicited adverse events were collected for no longer than 28 days.

Possible explanations for relatively high percentage of placebo recipients reporting adverse events:

The Nocebo Effect & side effects of normal saline injection.

"[T]he widely varying rates of adverse effects reported by patients taking placebo and the high prevalence of such symptoms in the general population should be considered by both trialists and clinicians. In addition, variability of adverse effect ascertainment is considerable and suggests the need for better standardization in research."

Source: Medication-Attributed Adverse Effects in Placebo Groups

Why placebo controlled trials are necessary.

Vaccine.Guide

Flublok by Protein Sciences Corporation (Quadrivalent Influenza)