How the pandemic changed, and measures to tackle delta

How the pandemic changed, and measures to tackle delta
© FREDERIC J. BROWN/AFP via Getty Images

On May 13, when approximately 116 million Americans, or 45.1 percent of the adult population, were fully vaccinated against COVID-19 and with case counts dropping to under 1,000 new cases diagnosed each day, Centers for Disease Control and Prevention (CDC) Director Rochelle WalenskyRochelle WalenskyWalensky says she will improve CDC messaging amid criticism Public health expert: Biden administration needs to have agencies on the 'same page' about COVID Child hospitalizations reach record high amid omicron surge: WSJ MORE made the announcement that, based on the data, fully vaccinated people no longer needed to wear a face mask or stay six feet away from others in most settings, whether outdoors or indoors.

“If you are fully vaccinated, you can start doing the things that you had stopped doing because of the pandemic. We have all longed for this moment when we can get back to some sense of normalcy,” said Walensky. The decision was supported by the available science that suggested fully vaccinated individuals were unlikely to be infected or transmit the SARS-CoV-2 virus even if infected.

Unfortunately, the people who should have continued to wear a mask did not and we were reminded once again how behavior cannot be easily changed by public health recommendations -- something that those of us working in HIV have known for a long time. Bottom line, if the CDC’s guidance had been followed and only fully vaccinated people removed their masks, we would be in a better place today.


What happened afterward is also interesting: The declining trend of infections continued for the next few weeks and dropped to an average of 500 new diagnoses per day. The data was so optimistic that, on July 4, President BidenJoe BidenMacro grid will keep the lights on Pelosi suggests filibuster supporters 'dishonor' MLK's legacy on voting rights Sanders calls out Manchin, Sinema ahead of filibuster showdown MORE celebrated the “Independence from COVID-19” saying that we were close to defeating this deadly virus, but also citing continued concern around the emergence of the Delta variant.

On the same day, during an annual gathering in Provincetown, Mass., where thousands gather every year to celebrate the Fourth of July, a superspreader event occurred that was a game changer.

It is estimated that over 75 percent of those in Provincetown to celebrate the holiday had received at least one dose of a COVID-19 vaccine and because of this, masks were not worn. What followed the celebrations was an abrupt increase in cases with over 1,000 cases having been connected to that celebration.

What was striking is that the great majority of cases occurred among vaccinated individuals. An epidemiologic investigation of the outbreak was published in the MMWR on July 30 and added two important facts: Most cases were due to the Delta variant and the amount of COVID-19 detected in samples obtained from those infected was the same whether you were vaccinated or not. So this told us a couple of things.

First, vaccinated people could get infected and they could transmit to others — the exact opposite from what we thought until then.

But it also told us that the vaccines are working. I’ll say it again: The vaccines demonstrated their efficacy because we also know that only a handful of those infected who were vaccinated required hospitalization and none died.

Outside of this specific event, other data tells us that the risk is not equal for vaccinated and unvaccinated persons and the risk of infection is eight times lower for vaccinated individuals. Similarly, the risk of severe disease and death is also much lower, in fact, 24 times lower.

What changed? The virus.

The Delta variant is much more transmissible than prior variants and this means more infections. The consequence and the challenge ahead are also concerning because, with nearly 100 million Americans eligible for vaccination but still unvaccinated, we will have a major wave of new infections, hospitalizations and deaths.

How about masks? The new CDC guidance says that everyone, whether you are vaccinated or not, should wear a mask indoors in public areas of substantial or high transmission.


Despite questions about how effective masking is, we know that, among many factors, mask compliance is the major one for transmission. If people do not wear masks, that crucial layer of protection does not exist. How good are masks in preventing transmission? Medical grade masks and cloth face coverings are 57 to 58 percent effective in protecting others and 37 to 50 percent effective in protecting the user. N95 masks are better, with 86 to 90 percent source-control efficacy and 96 to 99 percent personal- protection efficacy.

Thus, where masks are necessary (like, for example, when I am seeing a patient with COVID-19), a fitted N95 or its equivalent offers the highest level of protection.

At a population level, it has been estimated that if everyone wore a cloth mask, the transmission would be reduced by about 10 to 20 percent. While this may seem small, it is substantial when there is significant transmission.

A major limitation of mask mandates is that most transmission occurs in households and in family gatherings such as birthdays where masks are not worn. Thus, masks offer various levels of protection depending on the type of mask, the percent of the population wearing them and the specific setting. Therefore, it is important to accurately message the need for masking, but to also acknowledge its limited utility as an intervention.

While it is hard to predict the future, I am increasingly convinced that COVID-19 is here to stay. Our goal should be revised from ending transmission to decreasing disease and mortality. If we can bring deaths down to about 100 a day (about 36,000 per year), it will be equivalent to what we see with seasonal influenza.

Vaccines, and in particular the mRNA technology, will continue to be the game changer that gets us there. Mutations will continue until a critical mass are vaccinated globally. Populations with low vaccinations will have ongoing transmission and could end up creating entirely new strains. As a result, we will experience periods of more cases, more hospitalizations and more deaths and we will need to get used to masking recommendations during those periods.

As of now, all variants have been vaccine susceptible. Researchers around the world are working to develop new vaccines to address new variants. This is critical because if an entire new strain develops for which the vaccines are not effective, there will be a need for us to resume lockdowns. But if we do this right, with using masks and getting vaccinated, there will be no need for lockdowns and the U.S. economy will adapt and remain open -- but it may take vaccine and/or mask mandates to get us there.

The world has lived through pandemics since the beginning of time. The difference is that we never had a weapon as powerful as mRNA technology and the resulting vaccines, and masks were not as good or as widely available. 

Carlos del Rio, M.D., FIDSA, is vice president of the Infectious Diseases Society of America. He is a professor of medicine at Emory University School of Medicine and of global health and epidemiology at Emory’s Rollins School of Public Health, principal investigator and co-director of the Emory Center for AIDS Research, and co-principal investigator of the Emory-CDC HIV Clinical Trials Unit and Emory Vaccine and Treatment Evaluation Unit. He is also the international secretary of the National Academy of Medicine and the Chair of the PEPFAR Scientific Advisory Board.