The US Department of Defense (DoD) released a trove of files on UFOs. The files include images along with government documents and correspondence, some of which were classified until now.

“These files, hidden behind classifications, have long fueled justified speculation – and it’s time the American people see it for themselves,” said US Secretary of Defense Pete Hegseth in a statement on where the files are displayed.

The images are mostly photographs taken by members of the US military showing small dots or indistinct shapes in the sky. Of more interest are the hundreds of pages of files relating to UFOs, also called unidentified anomalous phenomena (UAPs), from the FBI, Air Force and various other government departments.

Many of the pages are correspondence between the government and concerned members of the public. Some are pamphlets from special-interest groups such as the Amalgamated Flying Saucer Clubs of America or the Fraternity of Cosmic Sons and Daughters, and others are requests from children to the head of the FBI – many to J. Edgar Hoover, who served in the role from 1935 to 1972 – for help with school projects.

Letters from UFO enthusiasts through the years, from the 1940s to now, show remarkable similarities in the sentiments they express: a feeling that UFO sightings have been mounting, that the government must be hiding something and that they are sure to be persecuted for saying as much.

The responses to these letters, and the internal government communications that have been released, seem to show something different – many thousands of reports of UFO sightings have been taken seriously and investigated, and there has been no indication that any of them have been extraterrestrial. This mirrors the 2023 results from NASA’s task force on UAPs, which found that normal aircraft and weather phenomena account for most reports, with only a few remaining unexplained due to blurry images and low-quality data.

The documents that have made the biggest splash are images and transcripts from NASA’s Gemini 7, Apollo 12 and Apollo 17 missions, each referencing some bright lights that the astronauts saw in space and could not explain. Most of these sightings have already been investigated and explained as micrometeoroid impacts on the moon or the spacecraft, bits of floating debris, and camera or film defects, although a few have remained unexplained thus far.

The DoD has opened a new investigation into the images that remain unexplained, and has been directed by the administration of President Donald Trump to “conduct separate reporting” on any unresolved UAP cases. According to the website, this is only the first of many rolling document drops expected “every few weeks” as more files are found and declassified.

The US health secretary claimed mRNA vaccines are ineffective against respiratory diseases, while announcing he was cutting half a billion dollars in funding for mRNA vaccine development. But this goes against the scientific evidence we have, which shows many mRNA vaccines work as well as – or better than – other types of vaccine. Here is what you need to know to assess these claims.

In announcing the cuts, the head of the US Department of Health and Human Services, Robert F Kennedy Jr,   “these vaccines fail to protect effectively against upper respiratory infections like COVID and flu”. Kennedy said the agency would shift funding “toward safer, broader vaccine platforms that remain effective even as viruses mutate”.

There is now a wide range of vaccine types: live viruses, killed viruses, genetically engineered viral shells, single viral proteins and mRNAs coding for viral proteins. The effectiveness of all of these kinds of vaccines often has a lot more to do with the nature of the virus being targeted than the vaccine itself.

For instance, the MMR vaccine can be 100 per cent effective at preventing measles outbreaks if more than about 90 per cent of a population is vaccinated. But the measles virus is an easy target because it does not change much and it takes a convoluted route deep inside the body, meaning there are plenty of opportunities for the immune system to intercept it before people develop symptoms or become infectious.

In contrast, the respiratory viruses that cause colds and flus first infect the cells lining the nose and throat. It is hard to generate high levels of effective antibodies in these membranes, so it is much more difficult to prevent infections and onward transmission than with measles.

Additionally, cold, flu and covid-19 viruses are constantly mutating, and there is strong evolutionary selection for any mutations that help a virus dodge the immune protection generated by infections or vaccinations. For this reason, no flu or covid-19 vaccine of any type provides the same lifelong protection as the measles component of the MMR vaccine. But the mRNA ones do work relatively well.

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For instance, some mRNA covid-19 vaccines were more than 90 per cent effective against symptomatic infections, with even higher protection against severe disease. For comparison, the effectiveness of the non-mRNA vaccines used to protect from the annual flu varies from 20 to 60 per cent. And in a recent trial, a combined covid-flu mRNA vaccine in people aged over 50 – those who most need protection.

So Kennedy’s claim of a lack of efficacy is nonsense. This is not to say mRNA vaccines are always better than other types. But new vaccines have to outperform older ones in trials – mRNA shots won’t get approved if they are not better.

Kennedy also claims other kinds of vaccines are more likely to remain effective as viruses mutate. This seems to be a reference to developing “universal vaccines” – a single vaccine that is effective against all flu viruses, say, or one that works against all coronaviruses. The idea is to target the outer parts of viruses that don’t change. But this is hard to do because viruses tend to hide their unchanging parts under the parts that do change.

Efforts to develop effective universal vaccines have so far failed, despite decades of efforts, so focusing too much funding on them could be a mistake. What is more, mRNA technology can, and already has, been used to create experimental universal vaccines. So the second part of Kennedy’s statement is also nonsense.

Last but not least, efficacy isn’t everything. Safety, cost and the speed of vaccine development are crucial, too. Here mRNA technology has some huge advantages. It is safer than vaccines consisting of actual viruses, cheaper than vaccines consisting of a single viral protein and can be developed much faster than either type – which is important with fast-changing respiratory viruses, especially in a pandemic situation.

In addition, the technology in mRNA vaccines could be used more broadly to develop a huge range of other treatments. The funding cuts announced by Kennedy on the basis of his false claim could slow development by deterring companies from investing in this approach.