Concerns Over COVID-19 Vaccine Efficacy and the Need for Boosters
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Chapter 1: Current Vaccine Efficacy Concerns
Countries are increasingly apprehensive that the effectiveness of COVID-19 vaccines may be diminishing. Although there are some troubling indicators, it remains uncertain if this is indeed the case. Last week, the CEO of Pfizer suggested that emerging data from Israel could imply a decline in vaccine antibodies, though specialists have expressed skepticism, as reported by Insider.
Patients are seen waiting for their third dose of the COVID-19 vaccine in Tel Aviv, Israel. Photo: Jack Guez/AFP via Getty Images
By Marianne Guenot
Health officials are starting to consider the possibility of administering third doses of coronavirus vaccines, highlighting the concern that two doses might not suffice. Recently, Pfizer announced its intention to seek approval for a third shot. Mikael Dolsten, the company's research and development director, stated that data from Israel might indicate a decrease in vaccine effectiveness among individuals vaccinated in January and February.
However, both the World Health Organization and U.S. public health authorities have asserted that the current data does not warrant the need for a booster shot yet. Evidence from Israel indicates a decline in vaccine efficacy.
In a recent report, the Israeli health ministry noted that the effectiveness of the Pfizer vaccine against infection and mild symptoms had decreased to 64% in June, down from previous highs exceeding 90%. This decline coincided with the spread of the Delta variant, which is known to be more resistant to vaccines, complicating efforts to pinpoint the exact cause of the decrease. Nevertheless, the vaccine continues to lower the risk of severe disease and hospitalization by 93%, according to the health ministry.
Israeli journalist Nadav Eyal, affiliated with Ynet news, released data that suggested diminishing immunity among the earliest vaccinated groups, depicted in the following graph:
Eyal cited the health ministry for this information, although officials have yet to verify its authenticity. The graph illustrates a higher rate of reinfection among individuals vaccinated in January compared to those vaccinated in March.
Meaghan Kall, an epidemiologist at Public Health England, also pointed out that preliminary data from the UK might indicate a decline in vaccine immunity. In the accompanying graph, the blue line represents infection rates among healthcare workers, 96% of whom are fully vaccinated.
"This could indicate waning immunity (HCW were among first vaccinated in Jan/Feb) or possible immune escape by the Delta variant," Kall remarked in a tweet.
Section 1.1: Exploring Possible Explanations
Several factors could explain the observed trends beyond just waning immunity. Professor Eyal Leshem, an infectious disease expert at Israel’s Sheba Medical Center, explained to Insider that it’s possible the Delta variant is circumventing the protective effects of the vaccines. Given that Israel prioritized vaccinations for its most vulnerable populations, those who received their shots in January might be more likely to get tested due to the risks associated with infection.
Shane Crotty, a virologist at the La Jolla Institute for Immunology in California, remains unconvinced by the data from Israel. Research published by Pfizer in April indicated that the vaccine maintained a 91% efficacy rate against infection six months post-second dose. "That’s about as good as you could possibly hope for," Crotty commented.
As detailed by Insider’s Dr. Catherine Schuster-Bruce, studies from other nations report much higher vaccine efficacy than that observed in Israel: 88% in a UK study published in May and 87% in a Canadian study released on July 4. "I value those findings more than the undisclosed, small-study data from Israel," Crotty noted.
Section 1.2: Longevity of Protection Against Severe Disease
Speaking with Bloomberg, Pfizer’s Dolsten remarked that the data from Israel could suggest a reduction in frontline antibodies. "When antibody levels are low, highly contagious viruses may reinfect and lead to mild cases," he explained. Nevertheless, he believes that protection against severe disease is likely to persist longer due to other immune responses at play.
Dolsten noted that a booster dose could potentially elevate antibody levels once more. Preliminary findings released by Pfizer indicate that a third dose may boost neutralizing antibody levels against the virus by five to ten times.
In conclusion, Leshem, the Israeli infectious disease expert, conveyed that the data from Israel should not be overly alarming. "There may be a decrease in antibodies and possibly a corresponding reduction in protection against infection, but it appears there is no significant decline in the most critical outcome: protection against hospitalization," he affirmed.
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