Still no data on Pfizer bivalent booster efficacy

By Anonymous Public Health Official

I recently got this submission from an anonymous public health official who plays a role in decision making. This is about the Pfizer press release for the bivalent booster. Some are claiming, based on this press release, that we have evidence of clinical efficacy. Nothing can be further from the truth.

We have non-specified antibody titer data. That's a surrogate endpoint. It doesn't have a one to one correlation with living longer or better. The correlation may vary by product, by dose, there may be effect modification or interaction with the number of doses, and it may vary by age of the person receiving it.

We simply don't know.

In the old days, doctors would admit that surrogate endpoints are often unreliable. Now public health officials lie about their confidence, and claim alternative views are misinformation.

I'm not surprised the public health official who wrote this chooses to be anonymous. To me, that's a scary indictment of science. A profession unwilling to debate or even think rationally. Obviously an 88-year-old has a different benefit risk profile than an 8-year-old. Saying that is controversial apparently.

Vinay Prasad

Still no data on Pfizer bivalent booster efficacy

On October 13, 2022 Pfizer and BioNTech published a press release announcing “Positive Early Data From Clinical Trial of Omicron BA.4/BA.5-Adapted Bivalent Booster in Individuals 18 Years and Older”.

This was hailed in some media like CNBC and Reuters as an evidence of the new booster effectiveness against Omicron BA.4 and BA.5 variants. As of October 17, there are no available publications in peer reviewed journals on this, so let’s look into the press release to assess the validity of the media claims.

In the press release Pfizer claims that bivalent booster “demonstrated a substantial increase in the Omicron BA.4/BA.5 neutralizing antibody response above pre-booster levels based on sera taken 7 days after administration” which was based on two groups of subjects aged 18-55 and 55+ years old.

However, they also noted that in 55+ years old bivalent booster “elicited more limited increases in the neutralizing antibody”. Pfizer didn’t publish any data on specific levels of antibody titers, so it is unknown how much is the increase in both 18-55 and 55+ years old group.

What can new derive from the available information is that:

1. there is an increase in neutralizing antibody levels after using bivalent booster,

2. lower antibody levels was seen in the 55+ years old group,

3. the exact antibody titers are unknown

4. there is no data on booster efficacy on infection prevention, transmission, mild and/or severe disease, hospitalization or death.

It is worth noting that neutralizing antibody levels aren’t linearly correlated with the clinical protection that the vaccines can provide.

The actual vaccine efficacy can be estimated when we have data on the outcomes such as severe illness or hospitalization.

As such this press release doesn’t provide data to claim that the bivalent booster is effective against Omicron BA.4 or BA.5 variants. Such media claims are misleading and set up yet another COVID-related false expectations trap in case the new booster doesn’t demonstrate real world effectiveness.

This already did and will impact public trust in vaccines with proven efficiency and Public Health policies.