The Shifting Narrative on Vaccine Effectiveness

A timeline of public statements by the US government

I’ve been working on this Substack article on-and-off for a while, but after seeing video today of Walensky lying to Congress, yet again, I decided to go ahead and wrap this up and send it out. While I believe it is reasonably complete, consider it a work in progress — I will update the timeline if I find out about any key statements that I think should be added. - Kelley

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Several major questions in the Covid-19 response revolve around what government officials knew and what was publicly known, especially in 2021, about the effectiveness of Covid vaccines. I’ve been combing through some of the CDC statements, video clips, and articles in mainstream media to put together a timeline of publicly available information about the “safe and effective” messaging of the Covid vaccines. This Substack will focus on statements about the vaccine’s effectiveness. Messaging around vaccine safety will be covered in a separate Substack.

“…data from the CDC today suggests, you know, that vaccinated people do not carry the virus, don’t get sick….” CDC Director, Dr. Rochelle Walensky on MSNBC, March 29, 2021 (transcript)

I aimed to write this primarily as a historical record. I have tried to avoid judgments about the accuracy of the statements, except to point out when the official claims are contradictory (which was quite common, unfortunately). And this isn’t meant to be an exhaustive list of all public claims by government officials, but if you think there are important statements missing, please let me know.

Important note: Vaccine efficacy and effectiveness are often used interchangeably, but there actually is a distinction. Efficacy is in trials, effectiveness is in the real world, and is typically lower. Read more in this explainer from Yale Medicine.

— 2020 —

November 2020: Pfizer vaccine achieved 95% efficacy against symptomatic COVID-19 in trials and Moderna vaccine achieved 94.5% efficacy against symptomatic COVID-19 in trials.

December 2020: FDA issues Emergency Use Authorization (EUA) for Pfizer-BioNTech COVID-19 vaccine (for ages 16+) & Moderna COVID-19 vaccine (for ages 18+) “for the prevention of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)”. It also stated, “At this time, data are not available to make a determination about how long the vaccine will provide protection, nor is there evidence that the vaccine prevents transmission of SARS-CoV-2 from person to person.”

“At this time, data are not available to make a determination about how long the vaccine will provide protection, nor is there evidence that the vaccine prevents transmission of SARS-CoV-2 from person to person.” (FDA)

— 2021 —

February 10, 2021: CDC says fully vaccinated people can skip quarantine (after an exposure), but only for the first 3 months after their second shot because “protection may wear off after three months.”

February 27, 2021: FDA issues Emergency Use Authorization (EUA) for Janssen (Johnson & Johnson) COVID-19 vaccine (for ages 18+), stating “Overall, the vaccine was approximately 67% effective in preventing moderate to severe/critical COVID-19.”
Like the initial Pfizer and Moderna press releases, it also said, “At this time, data are not available to determine how long the vaccine will provide protection, nor is there evidence that the vaccine prevents transmission of SARS-CoV-2 from person to person.”

March 8, 2021: A CDC Science Brief was created with “Rationale and Evidence for Public Health Recommendations for Fully Vaccinated People.” It stated “A growing body of evidence suggests that fully vaccinated people are less likely to have asymptomatic infection and potentially less likely to transmit SARS-CoV-2 to others. However, further investigation is ongoing.”

March 26, 2021: Fauci announced a study to determine if vaccinated people could transmit the virus. “This is a question of extreme importance,” Fauci said. (The study of college students was expected to take about five months, but it was never completed.)

THREE DAYS LATER…

March 29, 2021: CDC Director Walensky told Rachel Maddow on MSNBC that “…data from the CDC today suggests, you know, that vaccinated people do not carry the virus, don’t get sick….” The data she was referring to was this MMWR with interim estimates of vaccine effectiveness that had come out the same day and was the reason for her appearance on MSNBC.

THREE DAYS AFTER THAT…

April 1, 2021: A CDC spokesperson walked back comments Walensky made on Rachel Maddow’s show, telling the New York Times “The evidence isn’t clear whether they can spread the virus to others.”

New York Times, April 1, 2021

April 12, 2021: Fauci says there will be “there will be hundreds, and maybe thousands” of breakthrough infections.

THREE DAYS LATER…

April 15, 2021: CDC announces 5,800 breakthrough infections, and breakthroughs were described as “very rare”. The majority (71%) were symptomatic, and there were 396 hospitalizations and 74 deaths.

May 10, 2021: FDA expands the EUA of Pfizer-BioNTech COVID-19 vaccine for adolescents 12–15 years of age. This press release stated, “At this time, there are limited data to address whether the vaccine can prevent transmission of the virus from person to person. In addition, at this time, data are not available to determine how long the vaccine will provide protection.”

“At this time, there are limited data to address whether the vaccine can prevent transmission of the virus from person to person. In addition, at this time, data are not available to determine how long the vaccine will provide protection.” (FDA)

May 13, 2021: CDC lifted mask wearing guidance for vaccinated people, citing three studies that showed the vaccines were very effective.

May 16, 2021:

• CDC announces that 223 people who had breakthrough Covid cases have died. CDC Director Walensky was clear to explain that deaths with Covid do not necessarily mean the death was due to Covid.

• Fauci claimed vaccinated people become a “dead end to the virus” just two months after he said the question of transmission was of extreme importance and was being studied (with results not expected until fall).

May 19, 2021: CDC Director Walensky testified to a Senate committee that “Data have demonstrated even if you were to get infected during post-vaccination, you can’t give it to anyone else.”

May 27, 2021: A CDC Science Brief was updated with new evidence showing reduction of asymptomatic infections and lower viral load in vaccinated people, which “may indicate reduced transmissibility”. However, the conclusion section stated “Vaccinated people could potentially still become infected and spread the virus to others.” This is considerably less certain than recent comments by Walensky and Fauci.

CDC web site, from Wayback Machine (June 2, 2021)

July 21, 2021: Biden claimed at a CNN town hall, “If you’re vaccinated, you’re not going to be hospitalized, you’re not going to be in the ICU unit and you’re not going to die.” He later claimed, “You’re not going to get Covid if you have these vaccinations.” CNN fact checked these false statements.

July 27, 2021: CDC web site updated to say that “…data suggest lower effectiveness against confirmed infection and symptomatic disease caused by the Beta, Gamma, and Delta variants compared with the ancestral strain and Alpha variant.”

August 6, 2021: CDC Director Walensky tells CNN that the vaccines can no longer prevent transmission.

“Our vaccines are working exceptionally well,” Walensky told CNN’s Wolf Blitzer. “They continue to work well for Delta, with regard to severe illness and death – they prevent it. But what they can’t do anymore is prevent transmission.”
- CNN (August 6, 2021)

September 15, 2021: CDC web site updated again with additional information about vaccine effectiveness (VE) for the predominant Delta variant. “Infections with the Delta variant in vaccinated persons potentially have reduced transmissibility than infections in unvaccinated persons, although additional studies are needed.” It also stated: “Early evidence suggests infections in fully vaccinated persons caused by the Delta variant of SARS-CoV-2 may be transmissible to others; however, SARS-CoV-2 transmission between unvaccinated persons is the primary cause of continued spread.” [That last statement seems to lack quality supporting data. The CDC cited a preprint showing vaccinated individuals had lower forward transmission to their contacts with Delta, but the preprint was from China, where they use Sinopharm/Sinovac, not mRNA vaccines.]

October 25, 2021: Biden issues executive order requiring vaccination (primary series) for foreign travelers coming into the US, which states “…vaccination is the most important measure for reducing the risk of COVID-19 transmission and for avoiding severe illness, hospitalization, and death.” This contradicts Walensky’s statements about the vaccines on August 6, 2021, when she stated “what they can’t do anymore is prevent transmission.”

— 2022 —

March 3, 2022: CDC Director Walensky tells a group at Washington University that “nobody said waning” when the vaccines were new. This contradicts FDA press releases from Dec. 2020 and May 2021 about unknown duration of protection, as well as the Feb. 10, 2021 warning from CDC that “protection may wear off after three months.”

August 11, 2022: CDC updated guidance to remove distinction between vaccinated and unvaccinated people. The press release stated: “Protection provided by the current vaccine against symptomatic infection and transmission is less than that against severe disease and diminishes over time.” An MMWR about the new guidance stated more clearly: “Receipt of a primary series alone… provides minimal protection against infection and transmission.”

“Receipt of a primary series alone… provides minimal protection against infection and transmission.” (CDC MMWR)

— 2023 —

February 8, 2023: When asked about the vaccination requirement for foreign travelers, CDC Director Walensky testified to a Congressional committee that the vaccine “doesn't prevent transmission as well as it did for prior variants, but it does still prevent some.” This contradicts her statements on CNN from August 6, 2021, and the official CDC guidance from August 11, 2022.

April 19, 2023: When asked about whether vaccinated people carry the virus, CDC Director Walensky testified to a Congressional committee that in March 2021, “all the data at the time suggested that people who were vaccinated, even if they got sick, couldn’t transmit the virus to someone else.” This contradicts statements from Fauci, from CDC spokesperson, and from the CDC web site at the time, which said the data was not clear (see my timeline from Spring 2021 for details).