What to know about COVID-19, the Delta variant and vaccines as fall approaches

Severe cases remain rare, but mild infections are less uncommon.

While health officials say current data suggests the vaccines remain highly effective against severe disease, hospitalizations and death, spiking cases in the community and waning immunity from the vaccines have led to a growing number of fully vaccinated Americans reporting mostly mild cases of so-called "breakthrough" infections of COVID-19. 

Before the current surge in Delta variant cases, a preliminary calculation by the CDC estimated that more than 51,000 symptomatic cases of breakthrough infections had occurred among 77 million fully vaccinated people through April. 

Leaked slides from the CDC last month estimated that the pace of these symptomatic breakthrough cases had climbed to 35,000 per week among 162 million vaccinated Americans.

But a study released by the CDC this month found overall vaccine effectiveness against any infection appeared to drop further than many had previously expected through late July, down to 79.8% overall as the Delta variant surged around the country. In nursing homes, whose residents are especially vulnerable, the CDC estimated that the effectiveness of two doses of the Pfizer and Moderna shots against infection may have declined to 53.1%.

Those findings helped lead to the Biden administration's decision to recommend booster shots starting in September for most Americans eight months after their second dose.

On Monday, August 23, Pfizer and BioNTech became the first to gain full FDA approval for their COVID-19 vaccine. That's expected to lead more companies and schools to impose vaccination requirements.

The Biden administration's top health experts have predicted that, given the overwhelming real-world evidence of the safety and effectiveness of vaccines from Pfizer, Moderna and Johnson & Johnson, it is inevitable that they will all eventually win full approval. (They were rolled out to the public under what the FDA calls Emergency Use Authorization.)

However, FDA leaders had cautioned that — even with "sprint teams" deployed to accelerate inspections and detailed reviews of the drugmaker's data — moving the COVID-19 vaccines to full approval would take time.

Vetting each vaccine license application could take three to four months: the government must work with the drugmaker to resolve issues flagged at detailed inspections of vaccine factories around the world and examine the now massive safety monitoring databases for each shot.

Pfizer finished its application in May, placing it first in line for approval. Moderna says it hopes to complete its submission in August. A person familiar with the FDA's plans said Friday that the company had yet to complete its application.

It could take until the late fall or early winter for children as young as 5. Pfizer's vaccine is currently authorized for ages 12 and up, but all of the companies are running clinical trials in younger age groups.

After reports of rare cases of heart problems myocarditis and pericarditis surfaced among adolescents who received the COVID-19 vaccine, Moderna and Pfizer both said they were moving to accommodate new requests from the FDA to adjust their trials of the shots in younger children to look for rare side effects — a move that could delay completion of the trials.

Moderna disclosed earlier this month that it had expanded enrollment for its vaccine trial and added a new "adverse event of interest": myocarditis and pericarditis.

Pfizer also acknowledged the request from the FDA, but told investors last month it believed it could still gather enough data "in the September timeframe or immediately after summer."

A top FDA official recently said it would likely take only a few weeks for them to vet data for the vaccine in the next younger age group — 5 years old to 11 years old — after the drugmakers submit data from their trials. However, the process could take longer if worrying side effects are detected, prompting a meeting of the regulator's independent panel of vaccine advisers.

Unless you are immunocompromised, not for a few months.

While federal health authorities have yet to formally authorize and recommend booster shots for most healthy Americans, the Biden administration said this week that they had seen enough data to begin planning for the rollout of booster doses.

Pending regulatory sign-off, the White House hopes to begin offering booster shots to millions of Americans by the week of September 20th, for adults who completed their initial vaccination at least eight months prior.

That timeline means the Americans prioritized earliest for the initial vaccine rollout, like frontline health care workers or nursing home residents, will be the first ones eligible to receive boosters. 

Some Americans have already sought out their own unauthorized booster doses, though federal health officials warn they are neither needed nor recommended at the moment. 

The FDA still needs to scrutinize "safety signals" around any potential risks of an additional third shot, CDC Director Rochelle Walensky told CBSN, saying that the administration continues "to encourage people to wait for the third boost." 

In addition to concerns over tracking any potential safety issues from the third dose, the Biden administration's top doctors speculate that spacing out the third dose could help create more durable immunity, reducing the need for additional shots down the road.

Widely available COVID-19 tests can determine if you have the virus, but they cannot tell you which variant made you sick — that can only be determined by genomic sequencing of the virus in a lab. 

Earlier changes to the virus had raised concerns of a variant that might render some COVID-19 tests less effective. For example, the fast-spreading Alpha variant first spotted in the United Kingdom that dominated cases earlier this year was linked to a notorious "s-gene target failure" in some tests, though some scientists ended up using the errors as a shortcut to figuring out whether people had been sickened by the mutant strain. 

However, the Delta variant's characteristic mutations are not linked to the same kind of issues. In fact, some of Delta's signature features — like large amounts of infectious virus detectable in the nose — could make it easier for tests to spot it. 

Yes, although it's unclear how much the likelihood of hospitalization has increased.

Given how contagious the Delta variant is, public health officials had previously warned that more unvaccinated people falling ill from the virus would likely translate to more people in the hospital..

Now the pace of new hospital admissions of patients with COVID-19 has spiked in recent weeks, climbing to record highs for many age groups beyond the peaks of the deadly winter surge. Pediatric hospitals have reported an overwhelming surge of patients, in some cases beyond previous waves of the virus. 

Federal health officials have pointed to worrying data abroad showing an uptick in the risk of hospitalization from the virus overall. One study from Canada, which has yet to be peer-reviewed, found a "pronounced" increase in the risk of hospitalization and death.

However, compared to older groups, rates of COVID-19 associated hospitalization still appear to be smaller among children than adults. 

The Delta variant (B.1.617.2) has several sub-lineages (including AY.1, AY.2, and AY.3) that the CDC recently began itemizing separately on its estimates of currently circulating virus in the U.S.

Of those, the "Delta Plus" variant (AY.1) — which had initially raised alarm overseas, given a worrying mutation that might make it even more transmissible — appears not to have gained much of a foothold in the United States. 

AY.1 now makes up just 0.1% of circulating virus in the U.S., according to the CDC's latest estimate, with 23 states reporting at least one case.

Another sub-lineage, AY.3, has also grown to make up a significant share of circulating Delta variant cases in the United States. However, scientists say it is likely not more dangerous or fast-spreading than the main Delta strain. Scientists had separated it out as a sub-lineage of Delta merely to help public health officials track different waves of the virus in the U.S.

Estimates vary widely, but experts have speculated that the current surge will likely peak in different times in different places depending on when states adopt stronger public health measures and what share of the population is fully vaccinated or has already been infected by the virus. 

Many states are now predicted to see stable or falling hospitalization rates, according to the CDC-backed "national ensemble" forecast, after surges earlier this month. Meanwhile, others are still on track to reach record highs for the summer.

Nationwide, estimates from the forecast predict that the pace of new COVID-19 hospitalizations and deaths "will likely increase over the next 4 weeks" at least. 

"We are already on a trajectory that looks strikingly similar to the sharp incline that the U.K. saw," Dr. Anthony Fauci told an event hosted by the Centers for Strategic and International Studies earlier this month.

"We are going to be between 100- and 200,000 cases before this thing starts to turn around," Fauci added later.