In countries with high vaccination rates, such as the U.A.E., Chile and the Seychelles, we have seen an increase in infection. While some vaccines provide some protection, they don't eliminate the pandemic. Low-efficacy vaccines like Sinovacs Coronavac may not reduce asymptomatic spread.It is not surprising that the World Health Organization continues to recommend masking for people who have been vaccinated. They don't only advise countries that have the best vaccines. The CDC says they are not offering advice to the U.S., where mRNA vaccinations are primarily in use.Most places are now reopened. Many businesses are expected to return to their offices in the fall. Schools will be open. Already, leisure travel is back to pre-pandemic levels and in some cases has even exceeded it. Is this a sustainable trend?I have been an optimist guided by science. I predicted that a vaccine would be approved by the end of 2020, and then mass vaccinations could begin in spring 2021. However, I was too optimistic, as I didn't anticipate the level of effectiveness of the vaccines.Travel is not yet out of reach for two reasons.Leisure travel could dry up as summer winds down and people return to work. The fall is when airlines are more dependent on business travel. This has historically caused it to decline. Although business travel may be poised to make a comeback in fall, it will likely take some time and not play the same supporting role as it did previously. This could mean that current optimism about travel may be shattered when it becomes clear that it won't last through September, October, and until Thanksgiving. Variants can lead to fears of the virus keeping people at home or new restrictions. The U.K. is worried about a return to normal, even though their main vaccine performs better against the Chinese vaccines. Israel has seen an increase in cases despite having a better vaccine than the rest of the world.Although there were many scary stories about Israel's breakthrough infection, the high vaccination rate means that positive cases are more likely to be vaccinated than those who have not been vaccinated. Even in the U.K., a resurgence of the virus has not been accompanied with spike hospitalizations.The variants are still being resistant to the best vaccines. Breakthrough infections are rare, but not as severe as the rest. There are some anecdotal cases that they have been. Because older people are more likely to be vaccinated, cases tend to cluster among younger people who are less susceptible.However, the Delta virus variant could still be infected. This is especially true as we enter the fall and enjoy the seasonal transmission reduction.It is notable that the (super rough math) seems to work in this instance. Initial Rt = 1.1, which corresponds to close to the mathematical expectation of 18%. 6/16 Trevor Bedford (@trvrb), June 30, 2021Entering R0 of 1.18 into the epidemic size equation results in 29% of those infected by the Delta wave. 9/16 Trevor Bedford (@trvrb), June 30, 2021Back of the envelope estimates that 62% of the U.S. has immunity to vaccination or previous infection. This accounts for the possibility of breakthrough infections as well as the possibility of vaccination being more effective among people who have not had the virus. We would expect another 11% to be infected with the Delta variant, or 36 million people.This is the back of an envelope and things will not work out exactly as expected. Unvaccinated individuals may mix with those who have been vaccinated, but they won't be at risk. Some people may be immune even if they have not been vaccinated or are not protected by priority infections. It is a significant projection by order of magnitude and an actual scenario worth considering.Future infections will be more prevalent in younger people who are less likely to contract severe diseases. It will be concentrated in areas that have low immunity, such as the Southeast. The majority of spread in the U.K. is concentrated among the unvaccinated.Two-fold question surrounds travel.How will everyone react to the high level of virus transmission in their community, even those who have been vaccinated? They will limit their activities, even though they are at low risk due to highly effective vaccines. However, they are more at risk than if there was no virus. What will be the response of policymakers? Are they going to assume that everyone who doesn't get vaccinated is at risk? That hospitals won't be overwhelmed by the virus, which will most likely circulate among the younger population? Will they respond to the case numbers by imposing restrictions on indoor gatherings and re-imposing masking requirements, or What do you think?A virus resurgence may cause some people to avoid traveling. However, if you are unable to do certain activities or have to comply with restrictions, some people might choose to not travel.Spreading (largely) among unvaccinated may explain why policymakers continue to enforce the mask mandate beyond September 13, 2021, even for those who have been vaccinated. Another reason is the lobbying of airline unions to allow them to do so.The pandemic is not over in the U.S., or around the globe. Even though some of us who received mRNA vaccines from Moderna and Pfizer BioNTech appear to be protected against variants, we aren't done.
