Kansas Crimson

VACCINE DID REDUCE TRANSMISSION
Within months of the vaccine hitting the market, researchers in the UK (here) and Israel (here) began publishing studies suggesting that the Pfizer vaccine was reducing transmission of the virus.

In February 2021, for example, Israeli data (here) showed a sharp drop in infections among healthcare workers within 15-28 days of receiving the two-shot Pfizer vaccine series, indicating the vaccine was not just preventing symptomatic disease, but also preventing the virus from being passed from person to person.

“Whether it is 75 or 90 percent reduction doesn’t matter - it is a big drop in transmission,” Michal Linial, a professor of molecular biology and bioinformatics at Jerusalem’s Hebrew University, told Reuters at the time. “It means that not only is the individual vaccinated protected, the inoculation also provides protection to his or her surroundings” (here)

Evidence continued to build in 2021 that the mRNA-based vaccines prevented infections and onward transmission of the virus (here). But with the advent that year of the coronavirus Delta variant, plus waning immunity from vaccines delivered at the start of the year, protection against infection and transmission was seen to be dropping, although not eliminated, as previously described by Reuters Fact Check (here).

The newest family of Omicron variants has further eroded vaccine effectiveness against infection and transmission (here) . But even Omicron does not escape vaccine protection completely.

A recent study in U.S. prisons, for example, found that vaccinated people who experience an Omicron breakthrough infection still have lower odds of passing the virus to their contacts (here). The protection was seen to start waning quickly, though, the journal Nature reported: “For every 5 weeks that passed since a person’s last vaccine dose, the risk of transmitting the infection to a close contact increased by 6%” (here)

But studies did find that vaccinated people were much less likely to spread the virus, either because they were protected from getting infected in the first place, or by being less contagious if infected.

As we’ve reported, that became less true with the emergence of the more transmissible and immune evasive omicron variant, but there is still evidence that for a short period, vaccines help reduce omicron transmission somewhat.

“Being up to date with vaccination provides a transient period of increased protection against infection and transmission after the most recent dose, although protection can wane over time,” CDC experts wrote in their latest guidance for minimizing the impact of COVID-19.

In their commentary, Dean and Halloran mention two studies published in Science based on data from Israel to argue that there are multiple factors that affect the ability of COVID-19 vaccines to reduce transmission, such as time since vaccination and evasive variants.

One of the studies found that in households with one infected parent, the chances of at least one unvaccinated child becoming infected were much lower if that parent was vaccinated. The chance of infection was 72.1% lower with a vaccinated parent during the alpha period, shortly after the vaccines were rolled out, and 79.6% lower during the delta period. The other study found that vaccines reduce infectiousness by 23% using data from before the emergence of delta.

“COVID-19 vaccines have provided exceptional protection against severe disease, and they have reduced transmission. Notably, indirect protection is not all or nothing but rather incrementally increases with each newly immunized person. Ensuring our communities are well vaccinated is a major priority as SARS-CoV-2 becomes endemic,” Dean and Halloran concluded.

The fact that the Covid-19 vaccines did have an impact on transmission, particularly against the earliest variants, was verified with real world data after the vaccines were rolled out. Although the impact of vaccines on transmission has lessened against the Omicron variant, this does not mean that the vaccines impacting transmission was just a “myth” or “assumption”.

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Pfizer’s clinical trial results show the main measure analysed to determine whether the vaccine worked was symptomatic cases of lab-confirmed Covid-19. In the trial there were eight cases among vaccinated trialists and 162 among those given the placebo, indicating the vaccine was 95% effective.

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HEALTH / CORONAVIRUS
Claims that Pfizer vaccine wasn’t tested on preventing transmission need context
24 OCTOBER 2022
WHAT WAS CLAIMED
A Pfizer executive has admitted the company did not test whether its Covid-19 vaccine stopped transmission of the virus before its launch.

OUR VERDICT
Pfizer was always clear it did not test whether the vaccines reduced the risk of transmission among already-infected individuals. But the trial did show the vaccines reduced infection risk in the first place, so reduced the risk of onward infection.

“In COVID hearing, #Pfizer director admits: #vaccine was never tested on preventing transmission.”

ROB ROOS MEP, 11 OCTOBER 2022.
A claim by a member of the European Parliament (MEP) that an executive at Pfizer has revealed that Covid-19 vaccines weren’t tested for their impact on transmission is missing important context.

On 11 October, Dutch MEP Rob Roos tweeted a video clip from part of a Covid hearing at the European Parliament the previous day where he asked Janine Small, president of international markets at Pfizer, whether its Covid-19 vaccine was tested for its impact on transmission prior to its release.

Ms Small confirmed it was not tested in that way before release.

The video continues with Mr Roos addressing the camera to say: “This is scandalous. Millions of people worldwide felt forced to get vaccinated because of the myth that you do it for others. Now this turned out to be a cheap lie. This should be exposed."

At the time of writing, the post has been viewed more than 13 million times and retweeted more than 178,000 times. His comments have also attracted support from several prominent figures .

In an email to Full Fact, Mr Roos added: “Governments worldwide have introduced Covid mandates and passports that had an enormous impact on millions of people. They did so by explicitly arguing that vaccinated people cause less transmission of the virus. Ms. Small's response to my question proves this was an assumption by governments for which no evidence had been provided.”

However, Pfizer was not required to test the impact of its vaccine on transmission prior to its release.

A spokesperson from Pfizer told Full Fact by email: “The primary endpoints of our Covid-19 vaccine study were to evaluate the efficacy of the vaccine candidate in preventing Covid-19 disease in participants who had not been infected with the SARS-CoV-2 virus before they received the vaccine […]The trials were not designed to evaluate the vaccine’s effectiveness against transmission of SARS-CoV-2.”

The fact that the Covid-19 vaccines did have an impact on transmission, particularly against the earliest variants, was verified with real world data after the vaccines were rolled out. Although the impact of vaccines on transmission has lessened against the Omicron variant, this does not mean that the vaccines impacting transmission was just a “myth” or “assumption”.

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Transmission was not tested for
Despite Mr Roos presenting this as “breaking news”, Pfizer did not claim to have studied the issue before the vaccine’s market release.

Furthermore, the fact that the vaccine’s impact on transmission had not been assessed was already in the public domain.

On 3 December 2020, the day after the UK became the first country in the world to approve Pfizer's vaccine, CEO Albert Bourla told NBC News that the company had not investigated whether vaccinated people who became infected with the virus could pass it on to others.

He said: “I think this is something that needs to be examined. We are not certain about that right now.”

Similarly, when the US Food and Drug Administration (FDA) issued emergency approval for the Pfizer Covid vaccine on 11 December 2020 it noted there was no “evidence that the vaccine prevents transmission of SARS-CoV-2 from person to person.”

During a virtual meeting hosted by the European Medicines Agency on that same day, to discuss the development of all Covid vaccines, one presentation said the question of transmission remained “uncertain at approval" and would require "specific studies post approval".

In January 2021, the World Health Organisation (WHO) issued guidelines on the use of the Pfizer vaccine and noted there was “not yet any evidence of the effect of the vaccine on virus transmission”, recommending that other measures such as mask wearing and hand washing be continued to slow the spread of Covid.

The same WHO document also lists areas of research it recommends be pursued after the vaccine has been authorised. They include “studies to demonstrate whether this vaccine reduces SARS-CoV-2 transmission and viral shedding”.

Such reports make it clear Pfizer had not carried out tests to determine whether the vaccine stopped transmission prior to it being authorised, nor claimed to.

Pfizer’s clinical trial results show the main measure analysed to determine whether the vaccine worked was symptomatic cases of lab-confirmed Covid-19. In the trial there were eight cases among vaccinated trialists and 162 among those given the placebo, indicating the vaccine was 95% effective.

Impact on transmission
It’s important to note the difference between the technical definition of transmission used by Pfizer, and a more colloquial understanding of infection.

Pfizer’s trial did not look at whether or not infected people were more or less likely to pass the virus on to someone else, based on whether they were vaccinated or not.

But Pfizer’s trial did show that vaccination would lower your risk of being infected in the first place, and so would reduce the level of transmission. As the UK Health Security Agency said in its January 2022 vaccine surveillance report: “Uninfected individuals cannot transmit; therefore, the vaccines are also effective at preventing transmission.”

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Following the vaccine roll-out, some early real-world studies in the UK and Israel did seem to indicate that the vaccines reduced levels of transmission from those infected with the Alpha variant.

Later studies found the vaccines were less effective at preventing the transmission of subsequent variants of Covid-19 such as Delta and Omicron.

A study by the UK Health Security Agency found that two doses of the Pfizer vaccine initially reduced the transmission of the Delta variant by 31%.

A subsequent study of transmission of the Omicron variant in Denmark, reported in Nature, found that, due to its ability to evade prior immunity, vaccines were “less likely to be sufficient to curb transmission with Omicron compared to previous variants”.

While the vaccines do not eliminate all transmission, they can help. Studies done after distribution of the COVID-19 vaccines began, including research by Pfizer, did find that the company’s shot reduced asymptomatic infections in addition to symptomatic cases with earlier variants of the virus. Researchers in the United Kingdom reported in a February observational study that Pfizer’s vaccine helped cut transmission of the alpha and delta variants.

“Our study from earlier in the year shows that the Pfizer vaccine reduces transmission from people with breakthrough infections, at least in the 3 months post vaccine which we studied,” Dr. David Eyre, a professor of infectious diseases at the University of Oxford and lead author of the study, wrote in an email.

Experts have told the AP that while the original COVID-19 vaccines provide less protection against infection with the highly contagious omicron variant, they still protect against serious outcomes.

The CDC stated in an August report that receiving only the first one or two doses of a COVID-19 vaccine “provides minimal protection against infection and transmission” and that being up to date on all recommended booster doses “provides a transient period of increased protection against infection and transmission after the most recent dose, although protection can wane over time.

randylahey wrote: ↑Sun May 28, 2023 12:24 am You also insisted that covid19 was a natural mutation, and anyone who thought the global response indicated it might be a result of lab experimentation with viruses was just a conspiracy theorist

A few years later the scientific consensus is that it probably came from a lab

japhy wrote: ↑Sun May 28, 2023 10:05 am Nunca discuta con un tonto; los espectadores pueden no ser capaces de notar la diferencia.

PhDhawk wrote: ↑Sun May 28, 2023 12:35 am I'm going to go hang out with overlander.

Have fun guys.

Good luck with your mess pdub.

Feral wrote: ↑Sun May 28, 2023 10:42 am

japhy wrote: ↑Sun May 28, 2023 10:05 am Nunca discuta con un tonto; los espectadores pueden no ser capaces de notar la diferencia.

"Nunca luches con un cerdo, ambos se ensuciarán, y al cerdo le gusta"?

randylahey wrote: ↑Sat May 27, 2023 11:35 pm

pdub wrote: ↑Sat May 27, 2023 11:28 pm I got flak for letting you and lobster post.


I’m fine with that.

That doesn’t mean I agree with you morans.

I ended up being right about things they didn't want you to allow me to post though. It just goes to show where some of these other guys are at. I have never once asked for or expected anyone else to be silenced

People who have opinions different than mine should still be allowed to share them

Overlander wrote: ↑Sat May 27, 2023 10:20 pm
Randall seriously makes this entire board nearly unbearable.